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<head>
  <title>C++/Tree Mapping User Manual</title>

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  <div id="titlepage">
    <div id="title">C++/Tree Mapping User Manual</div>

  <p>Copyright &copy; 2005-2017 CODE SYNTHESIS TOOLS CC</p>

  <p>Permission is granted to copy, distribute and/or modify this
     document under the terms of the
     <a href="https://www.codesynthesis.com/licenses/fdl-1.2.txt">GNU Free
     Documentation License, version 1.2</a>; with no Invariant Sections,
     no Front-Cover Texts and no Back-Cover Texts.
  </p>

  <p>This document is available in the following formats:
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/index.xhtml">XHTML</a>,
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/cxx-tree-manual.pdf">PDF</a>, and
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/cxx-tree-manual.ps">PostScript</a>.</p>
  </div>

  <h1>Table of Contents</h1>

  <table class="toc">
    <tr>
      <th></th><td><a href="#0">Preface</a>
        <table class="toc">
          <tr><th></th><td><a href="#0.1">About This Document</a></td></tr>
	  <tr><th></th><td><a href="#0.2">More Information</a></td></tr>
        </table>
      </td>
    </tr>

    <tr>
      <th>1</th><td><a href="#1">Introduction</a></td>
    </tr>

    <tr>
      <th>2</th><td><a href="#2">C++/Tree Mapping</a>
        <table class="toc">
          <tr>
            <th>2.1</th><td><a href="#2.1">Preliminary Information</a>
              <table class="toc">
		<tr><th>2.1.1</th><td><a href="#2.1.1">C++ Standard</a></td></tr>
                <tr><th>2.1.2</th><td><a href="#2.1.2">Identifiers</a></td></tr>
                <tr><th>2.1.3</th><td><a href="#2.1.3">Character Type and Encoding</a></td></tr>
                <tr><th>2.1.4</th><td><a href="#2.1.4">XML Schema Namespace</a></td></tr>
		<tr><th>2.1.5</th><td><a href="#2.1.5">Anonymous Types</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.2</th><td><a href="#2.2">Error Handling</a>
              <table class="toc">
                <tr><th>2.2.1</th><td><a href="#2.2.1"><code>xml_schema::duplicate_id</code></a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.3</th><td><a href="#2.3">Mapping for <code>import</code> and <code>include</code></a>
              <table class="toc">
                <tr><th>2.3.1</th><td><a href="#2.3.1">Import</a></td></tr>
		<tr><th>2.3.2</th><td><a href="#2.3.2">Inclusion with Target Namespace</a></td></tr>
		<tr><th>2.3.3</th><td><a href="#2.3.3">Inclusion without Target Namespace</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.4</th><td><a href="#2.4">Mapping for Namespaces</a></td>
          </tr>
          <tr>
            <th>2.5</th><td><a href="#2.5">Mapping for Built-in Data Types</a>
              <table class="toc">
                <tr><th>2.5.1</th><td><a href="#2.5.1">Inheritance from Built-in Data Types</a></td></tr>
                <tr><th>2.5.2</th><td><a href="#2.5.2">Mapping for <code>anyType</code></a></td></tr>
                <tr><th>2.5.3</th><td><a href="#2.5.3">Mapping for <code>anySimpleType</code></a></td></tr>
                <tr><th>2.5.4</th><td><a href="#2.5.4">Mapping for <code>QName</code></a></td></tr>
                <tr><th>2.5.5</th><td><a href="#2.5.5">Mapping for <code>IDREF</code></a></td></tr>
		<tr><th>2.5.6</th><td><a href="#2.5.6">Mapping for <code>base64Binary</code> and <code>hexBinary</code></a></td></tr>
		<tr><th>2.5.7</th><td><a href="#2.5.7">Time Zone Representation</a></td></tr>
		<tr><th>2.5.8</th><td><a href="#2.5.8">Mapping for <code>date</code></a></td></tr>
		<tr><th>2.5.9</th><td><a href="#2.5.9">Mapping for <code>dateTime</code></a></td></tr>
		<tr><th>2.5.10</th><td><a href="#2.5.10">Mapping for <code>duration</code></a></td></tr>
		<tr><th>2.5.11</th><td><a href="#2.5.11">Mapping for <code>gDay</code></a></td></tr>
		<tr><th>2.5.12</th><td><a href="#2.5.12">Mapping for <code>gMonth</code></a></td></tr>
		<tr><th>2.5.13</th><td><a href="#2.5.13">Mapping for <code>gMonthDay</code></a></td></tr>
		<tr><th>2.5.14</th><td><a href="#2.5.14">Mapping for <code>gYear</code></a></td></tr>
		<tr><th>2.5.15</th><td><a href="#2.5.15">Mapping for <code>gYearMonth</code></a></td></tr>
		<tr><th>2.5.16</th><td><a href="#2.5.16">Mapping for <code>time</code></a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.6</th><td><a href="#2.6">Mapping for Simple Types</a>
              <table class="toc">
                <tr><th>2.6.1</th><td><a href="#2.6.1">Mapping for Derivation by Restriction</a></td></tr>
                <tr><th>2.6.2</th><td><a href="#2.6.2">Mapping for Enumerations</a></td></tr>
                <tr><th>2.6.3</th><td><a href="#2.6.3">Mapping for Derivation by List</a></td></tr>
                <tr><th>2.6.4</th><td><a href="#2.6.4">Mapping for Derivation by Union</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.7</th><td><a href="#2.7">Mapping for Complex Types</a>
              <table class="toc">
	        <tr><th>2.7.1</th><td><a href="#2.7.1">Mapping for Derivation by Extension</a></td></tr>
                <tr><th>2.7.2</th><td><a href="#2.7.2">Mapping for Derivation by Restriction</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.8</th><td><a href="#2.8">Mapping for Local Elements and Attributes</a>
              <table class="toc">
	        <tr><th>2.8.1</th><td><a href="#2.8.1">Mapping for Members with the One Cardinality Class</a></td></tr>
	        <tr><th>2.8.2</th><td><a href="#2.8.2">Mapping for Members with the Optional Cardinality Class</a></td></tr>
	        <tr><th>2.8.3</th><td><a href="#2.8.3">Mapping for Members with the Sequence Cardinality Class</a></td></tr>
		<tr><th>2.8.4</th><td><a href="#2.8.4">Element Order</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.9</th><td><a href="#2.9">Mapping for Global Elements</a>
              <table class="toc">
	        <tr><th>2.9.1</th><td><a href="#2.9.1">Element Types</a></td></tr>
	        <tr><th>2.9.2</th><td><a href="#2.9.2">Element Map</a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>2.10</th><td><a href="#2.10">Mapping for Global Attributes</a></td>
          </tr>
          <tr>
            <th>2.11</th><td><a href="#2.11">Mapping for <code>xsi:type</code> and Substitution Groups</a></td>
          </tr>
          <tr>
            <th>2.12</th><td><a href="#2.12">Mapping for <code>any</code> and <code>anyAttribute</code></a>
              <table class="toc">
	        <tr><th>2.12.1</th><td><a href="#2.12.1">Mapping for <code>any</code> with the One Cardinality Class</a></td></tr>
	        <tr><th>2.12.2</th><td><a href="#2.12.2">Mapping for <code>any</code> with the Optional Cardinality Class</a></td></tr>
	        <tr><th>2.12.3</th><td><a href="#2.12.3">Mapping for <code>any</code> with the Sequence Cardinality Class</a></td></tr>
		<tr><th>2.12.4</th><td><a href="#2.12.4">Element Wildcard Order</a></td></tr>
		<tr><th>2.12.5</th><td><a href="#2.12.5">Mapping for <code>anyAttribute</code></a></td></tr>
              </table>
            </td>
          </tr>
	  <tr>
            <th>2.13</th><td><a href="#2.13">Mapping for Mixed Content Models</a></td>
          </tr>
        </table>
      </td>
    </tr>

    <tr>
      <th>3</th><td><a href="#3">Parsing</a>
        <table class="toc">
          <tr>
            <th>3.1</th><td><a href="#3.1">Initializing the Xerces-C++ Runtime</a></td>
          </tr>
          <tr>
            <th>3.2</th><td><a href="#3.2">Flags and Properties</a></td>
          </tr>
          <tr>
            <th>3.3</th><td><a href="#3.3">Error Handling</a>
              <table class="toc">
	        <tr><th>3.3.1</th><td><a href="#3.3.1"><code>xml_schema::parsing</code></a></td></tr>
	        <tr><th>3.3.2</th><td><a href="#3.3.2"><code>xml_schema::expected_element</code></a></td></tr>
	        <tr><th>3.3.3</th><td><a href="#3.3.3"><code>xml_schema::unexpected_element</code></a></td></tr>
	        <tr><th>3.3.4</th><td><a href="#3.3.4"><code>xml_schema::expected_attribute</code></a></td></tr>
	        <tr><th>3.3.5</th><td><a href="#3.3.5"><code>xml_schema::unexpected_enumerator</code></a></td></tr>
		<tr><th>3.3.6</th><td><a href="#3.3.6"><code>xml_schema::expected_text_content</code></a></td></tr>
	        <tr><th>3.3.7</th><td><a href="#3.3.7"><code>xml_schema::no_type_info</code></a></td></tr>
	        <tr><th>3.3.8</th><td><a href="#3.3.8"><code>xml_schema::not_derived</code></a></td></tr>
		<tr><th>3.3.9</th><td><a href="#3.3.9"><code>xml_schema::not_prefix_mapping</code></a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>3.4</th><td><a href="#3.4">Reading from a Local File or URI</a></td>
          </tr>
          <tr>
            <th>3.5</th><td><a href="#3.5">Reading from <code>std::istream</code></a></td>
          </tr>
          <tr>
            <th>3.6</th><td><a href="#3.6">Reading from <code>xercesc::InputSource</code></a></td>
          </tr>
          <tr>
            <th>3.7</th><td><a href="#3.7">Reading from DOM</a></td>
          </tr>
        </table>
      </td>
    </tr>

    <tr>
      <th>4</th><td><a href="#4">Serialization</a>
        <table class="toc">
          <tr>
            <th>4.1</th><td><a href="#4.1">Initializing the Xerces-C++ Runtime</a></td>
          </tr>
          <tr>
            <th>4.2</th><td><a href="#4.2">Namespace Infomap and Character Encoding</a></td>
          </tr>
          <tr>
            <th>4.3</th><td><a href="#4.3">Flags</a></td>
          </tr>
          <tr>
            <th>4.4</th><td><a href="#4.4">Error Handling</a>
              <table class="toc">
	        <tr><th>4.4.1</th><td><a href="#4.4.1"><code>xml_schema::serialization</code></a></td></tr>
		<tr><th>4.4.2</th><td><a href="#4.4.2"><code>xml_schema::unexpected_element</code></a></td></tr>
		<tr><th>4.4.3</th><td><a href="#4.4.3"><code>xml_schema::no_type_info</code></a></td></tr>
              </table>
            </td>
          </tr>
          <tr>
            <th>4.5</th><td><a href="#4.5">Serializing to <code>std::ostream</code></a></td>
          </tr>
          <tr>
            <th>4.6</th><td><a href="#4.6">Serializing to <code>xercesc::XMLFormatTarget</code></a></td>
          </tr>
          <tr>
            <th>4.7</th><td><a href="#4.7">Serializing to DOM</a></td>
          </tr>
        </table>
      </td>
    </tr>

    <tr>
      <th>5</th><td><a href="#5">Additional Functionality</a>
        <table class="toc">
          <tr>
            <th>5.1</th><td><a href="#5.1">DOM Association</a></td>
          </tr>
          <tr>
            <th>5.2</th><td><a href="#5.2">Binary Serialization</a></td>
          </tr>
        </table>
      </td>
    </tr>

    <tr>
      <th></th><td><a href="#A">Appendix A &mdash; Default and Fixed Values</a></td>
    </tr>

  </table>
  </div>

  <h1><a name="0">Preface</a></h1>

  <h2><a name="0.1">About This Document</a></h2>

  <p>This document describes the mapping of W3C XML Schema
     to the C++ programming language as implemented by
     <a href="https://www.codesynthesis.com/products/xsd">CodeSynthesis
     XSD</a> - an XML Schema to C++ data binding compiler. The mapping
     represents information stored in XML instance documents as a
     statically-typed, tree-like in-memory data structure and is
     called C++/Tree.
  </p>

  <p>Revision 4.1.0<br/> <!-- Remember to change revision in other places -->
     This revision of the manual describes the C++/Tree
     mapping as implemented by CodeSynthesis XSD version 4.1.0.
  </p>

  <p>This document is available in the following formats:
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/index.xhtml">XHTML</a>,
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/cxx-tree-manual.pdf">PDF</a>, and
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/manual/cxx-tree-manual.ps">PostScript</a>.</p>

  <h2><a name="0.2">More Information</a></h2>

  <p>Beyond this manual, you may also find the following sources of
     information useful:</p>

  <ul class="list">
    <li><a href="https://www.codesynthesis.com/projects/xsd/documentation/cxx/tree/guide/">C++/Tree
        Mapping Getting Started Guide</a></li>

    <li><a href="http://wiki.codesynthesis.com/Tree/Customization_guide">C++/Tree
        Mapping Customization Guide</a></li>

    <li><a href="http://wiki.codesynthesis.com/Tree/FAQ">C++/Tree
        Mapping Frequently Asked Questions (FAQ)</a></li>

    <li><a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
        Compiler Command Line Manual</a></li>

    <li>The <code>examples/cxx/tree/</code> directory in the XSD
        distribution contains a collection of examples and a README
        file with an overview of each example.</li>

    <li>The <code>README</code> file in the XSD distribution explains
        how to compile the examples on various platforms.</li>

    <li>The <a href="https://www.codesynthesis.com/mailman/listinfo/xsd-users">xsd-users</a>
        mailing list is a place to ask questions. Furthermore the
        <a href="https://www.codesynthesis.com/pipermail/xsd-users/">archives</a>
        may already have answers to some of your questions.</li>
  </ul>


  <h1><a name="1">1 Introduction</a></h1>

  <p>C++/Tree is a W3C XML Schema to C++ mapping that represents the
     data stored in XML as a statically-typed, vocabulary-specific
     object model. Based on a formal description of an XML vocabulary
     (schema), the C++/Tree mapping produces a tree-like data structure
     suitable for in-memory processing as well as XML parsing and
     serialization code.</p>

  <p>A typical application that processes XML documents usually
     performs the following three steps: it first reads (parses) an XML
     instance document to an object model, it then performs
     some useful computations on that model which may involve
     modification of the model, and finally it may write (serialize)
     the modified object model back to XML.
  </p>

  <p>The C++/Tree mapping consists of C++ types that represent the
     given vocabulary (<a href="#2">Chapter 2, "C++/Tree Mapping"</a>),
     a set of parsing functions that convert XML documents to
     a tree-like in-memory data structure (<a href="#3">Chapter 3,
     "Parsing"</a>), and a set of serialization functions that convert
     the object model back to XML (<a href="#4">Chapter 4,
     "Serialization"</a>). Furthermore, the mapping provides a number
     of additional features, such as DOM association and binary
     serialization, that can be useful in some applications
     (<a href="#5">Chapter 5, "Additional Functionality"</a>).
  </p>


  <!-- Chapter 2 -->


  <h1><a name="2">2 C++/Tree Mapping</a></h1>

  <h2><a name="2.1">2.1 Preliminary Information</a></h2>

  <h3><a name="2.1.1">2.1.1 C++ Standard</a></h3>

  <p>The C++/Tree mapping provides support for ISO/IEC C++ 1998/2003 (C++98)
     and ISO/IEC C++ 2011 (C++11). To select the C++ standard for the
     generated code we use the <code>--std</code> XSD compiler command
     line option. While the majority of the examples in this manual use
     C++98, support for the new functionality and library components
     introduced in C++11 are discussed throughout the document.</p>

  <h3><a name="2.1.2">2.1.2 Identifiers</a></h3>

  <p>XML Schema names may happen to be reserved C++ keywords or contain
     characters that are illegal in C++ identifiers. To avoid C++ compilation
     problems, such names are changed (escaped) when mapped to C++. If an
     XML Schema name is a C++ keyword, the "_" suffix is added to it. All
     character of an XML Schema name that are not allowed in C++ identifiers
     are replaced with "_".
  </p>

  <p>For example, XML Schema name <code>try</code> will be mapped to
     C++ identifier <code>try_</code>. Similarly, XML Schema name
     <code>strange.na-me</code> will be mapped to C++ identifier
     <code>strange_na_me</code>.
  </p>

  <p>Furthermore, conflicts between type names and function names in the
     same scope are resolved using name escaping. Such conflicts include
     both a global element (which is mapped to a set of parsing and/or
     serialization functions or element types, see <a href="#2.9">Section
     2.9, "Mapping for Global Elements"</a>) and a global type sharing the
     same name as well as a local element or attribute inside a type having
     the same name as the type itself.</p>

  <p>For example, if we had a global type <code>catalog</code>
     and a global element with the same name then the type would be
     mapped to a C++ class with name <code>catalog</code> while the
     parsing functions corresponding to the global element would have
     their names escaped as <code>catalog_</code>.
  </p>

  <p>By default the mapping uses the so-called K&amp;R (Kernighan and
     Ritchie) identifier naming convention which is also used throughout
     this manual. In this convention both type and function names are in
     lower case and words are separated by underscores. If your application
     code or schemas use a different notation, you may want to change the
     naming convention used by the mapping for consistency.
     The compiler supports a set of widely-used naming conventions
     that you can select with the <code>--type-naming</code> and
     <code>--function-naming</code> options. You can also further
     refine one of the predefined conventions or create a completely
     custom naming scheme by using the  <code>--*-regex</code> options.
     For more detailed information on these options refer to the NAMING
     CONVENTION section in the <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a>.</p>

  <h3><a name="2.1.3">2.1.3 Character Type and Encoding</a></h3>

  <p>The code that implements the mapping, depending on the
     <code>--char-type</code>  option, is generated using either
     <code>char</code> or <code>wchar_t</code> as the character
     type. In this document code samples use symbol <code>C</code>
     to refer to the character type you have selected when translating
     your schemas, for example <code>std::basic_string&lt;C></code>.
  </p>

  <p>Another aspect of the mapping that depends on the character type
     is character encoding. For the <code>char</code> character type
     the default encoding is UTF-8. Other supported encodings are
     ISO-8859-1, Xerces-C++ Local Code Page (LPC), as well as
     custom encodings and can be selected with the
     <code>--char-encoding</code> command line option.</p>

  <p>For the <code>wchar_t</code> character type the encoding is
     automatically selected between UTF-16 and UTF-32/UCS-4 depending
     on the size of the <code>wchar_t</code> type. On some platforms
     (for example, Windows with Visual C++ and AIX with IBM XL C++)
     <code>wchar_t</code> is 2 bytes long. For these platforms the
     encoding is UTF-16. On other platforms <code>wchar_t</code> is 4 bytes
     long and UTF-32/UCS-4 is used.</p>

  <h3><a name="2.1.4">2.1.4 XML Schema Namespace</a></h3>

  <p>The mapping relies on some predefined types, classes, and functions
     that are logically defined in the XML Schema namespace reserved for
     the XML Schema language (<code>http://www.w3.org/2001/XMLSchema</code>).
     By default, this namespace is mapped to C++ namespace
     <code>xml_schema</code>. It is automatically accessible
     from a C++ compilation unit that includes a header file generated
     from an XML Schema definition.
  </p>

  <p>Note that, if desired, the default mapping of this namespace can be
     changed as described in <a href="#2.4">Section 2.4, "Mapping for
     Namespaces"</a>.
  </p>


  <h3><a name="2.1.5">2.1.5 Anonymous Types</a></h3>

  <p>For the purpose of code generation, anonymous types defined in
     XML Schema are automatically assigned names that are derived
     from enclosing attributes and elements. Otherwise, such types
     follows standard mapping rules for simple and complex type
     definitions (see <a href="#2.6">Section 2.6, "Mapping for Simple Types"</a>
     and <a href="#2.7">Section 2.7, "Mapping for Complex Types"</a>).
     For example, in the following schema fragment:
  </p>

  <pre class="xml">
&lt;element name="object">
  &lt;complexType>
    ...
  &lt;/complexType>
&lt;/element>
  </pre>

  <p>The anonymous type defined inside element <code>object</code> will
     be given name <code>object</code>. The compiler has a number of
     options that control the process of anonymous type naming. For more
     information refer to the <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a>.</p>


  <h2><a name="2.2">2.2 Error Handling</a></h2>

  <p>The mapping uses the C++ exception handling mechanism as a primary way
     of reporting error conditions. All exceptions that are specified in
     this mapping derive from <code>xml_schema::exception</code> which
     itself is derived from <code>std::exception</code>:
  </p>

  <pre class="c++">
struct exception: virtual std::exception
{
  friend
  std::basic_ostream&lt;C>&amp;
  operator&lt;&lt; (std::basic_ostream&lt;C>&amp; os, const exception&amp; e)
  {
    e.print (os);
    return os;
  }

protected:
  virtual void
  print (std::basic_ostream&lt;C>&amp;) const = 0;
};
  </pre>

  <p>The exception hierarchy supports "virtual" <code>operator&lt;&lt;</code>
     which allows you to obtain diagnostics corresponding to the thrown
     exception using the base exception interface. For example:</p>

  <pre class="c++">
try
{
  ...
}
catch (const xml_schema::exception&amp; e)
{
  cerr &lt;&lt; e &lt;&lt; endl;
}
  </pre>

  <p>The following sub-sections describe exceptions thrown by the
     types that constitute the object model.
     <a href="#3.3">Section 3.3, "Error Handling"</a> of
     <a href="#3">Chapter 3, "Parsing"</a> describes exceptions
     and error handling mechanisms specific to the parsing functions.
     <a href="#4.4">Section 4.4, "Error Handling"</a> of
     <a href="#4">Chapter 4, "Serialization"</a> describes exceptions
     and error handling mechanisms specific to the serialization functions.
  </p>


  <h3><a name="2.2.1">2.2.1 <code>xml_schema::duplicate_id</code></a></h3>

  <pre class="c++">
struct duplicate_id: virtual exception
{
  duplicate_id (const std::basic_string&lt;C>&amp; id);

  const std::basic_string&lt;C>&amp;
  id () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::duplicate_id</code> is thrown when
     a conflicting instance of <code>xml_schema::id</code> (see
     <a href="#2.5">Section 2.5, "Mapping for Built-in Data Types"</a>)
     is added to a tree. The offending ID value can be obtained using
     the <code>id</code> function.
  </p>

  <h2><a name="2.3">2.3 Mapping for <code>import</code> and <code>include</code></a></h2>

  <h3><a name="2.3.1">2.3.1 Import</a></h3>

  <p>The XML Schema <code>import</code> element is mapped to the C++
     Preprocessor <code>#include</code> directive. The value of
     the <code>schemaLocation</code> attribute is used to derive
     the name of the header file that appears in the <code>#include</code>
     directive. For instance:
  </p>

  <pre class="xml">
&lt;import namespace="https://www.codesynthesis.com/test"
        schemaLocation="test.xsd"/>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
#include "test.hxx"
  </pre>

  <p>Note that you will need to compile imported schemas separately
     in order to produce corresponding header files.</p>

  <h3><a name="2.3.2">2.3.2 Inclusion with Target Namespace</a></h3>

  <p>The XML Schema <code>include</code> element which refers to a schema
     with a target namespace or appears in a schema without a target namespace
     follows the same mapping rules as the <code>import</code> element,
     see <a href="#2.3.1">Section 2.3.1, "Import"</a>.
  </p>

  <h3><a name="2.3.3">2.3.3 Inclusion without Target Namespace</a></h3>

  <p>For the XML Schema <code>include</code> element which refers to a schema
     without a target namespace and appears in a schema with a target
     namespace (such inclusion sometimes called "chameleon inclusion"),
     declarations and definitions from the included schema are generated
     in-line in the namespace of the including schema as if they were
     declared and defined there verbatim. For example, consider the
     following two schemas:
  </p>

  <pre class="xml">
&lt;-- common.xsd -->
&lt;schema>
  &lt;complexType name="type">
  ...
  &lt;/complexType>
&lt;/schema>

&lt;-- test.xsd -->
&lt;schema targetNamespace="https://www.codesynthesis.com/test">
  &lt;include schemaLocation="common.xsd"/>
&lt;/schema>
  </pre>

  <p>The fragment of interest from the generated header file for
     <code>text.xsd</code> would look like this:</p>

  <pre class="c++">
// test.hxx
namespace test
{
  class type
  {
    ...
  };
}
  </pre>

  <h2><a name="2.4">2.4 Mapping for Namespaces</a></h2>

  <p>An XML Schema namespace is mapped to one or more nested C++
     namespaces. XML Schema namespaces are identified by URIs.
     By default, a namespace URI is mapped to a sequence of
     C++ namespace names by removing the protocol and host parts
     and splitting the rest into a sequence of names with '<code>/</code>'
     as the name separator. For instance:
  </p>

  <pre class="xml">
&lt;schema targetNamespace="https://www.codesynthesis.com/system/test">
  ...
&lt;/schema>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
namespace system
{
  namespace test
  {
    ...
  }
}
  </pre>

  <p>The default mapping of namespace URIs to C++ namespace names can be
     altered using the <code>--namespace-map</code> and
     <code>--namespace-regex</code> options. See  the
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a> for more information.
  </p>

  <h2><a name="2.5">2.5 Mapping for Built-in Data Types</a></h2>

  <p>The mapping of XML Schema built-in data types to C++ types is
     summarized in the table below.</p>

  <!-- border="1" is necessary for html2ps -->
  <table id="builtin" border="1">
    <tr>
      <th>XML Schema type</th>
      <th>Alias in the <code>xml_schema</code> namespace</th>
      <th>C++ type</th>
    </tr>

    <tr>
      <th colspan="3">anyType and anySimpleType types</th>
    </tr>
    <tr>
      <td><code>anyType</code></td>
      <td><code>type</code></td>
      <td><a href="#2.5.2">Section 2.5.2, "Mapping for <code>anyType</code>"</a></td>
    </tr>
    <tr>
      <td><code>anySimpleType</code></td>
      <td><code>simple_type</code></td>
      <td><a href="#2.5.3">Section 2.5.3, "Mapping for <code>anySimpleType</code>"</a></td>
    </tr>

    <tr>
      <th colspan="3">fixed-length integral types</th>
    </tr>
    <!-- 8-bit -->
    <tr>
      <td><code>byte</code></td>
      <td><code>byte</code></td>
      <td><code>signed&nbsp;char</code></td>
    </tr>
    <tr>
      <td><code>unsignedByte</code></td>
      <td><code>unsigned_byte</code></td>
      <td><code>unsigned&nbsp;char</code></td>
    </tr>

    <!-- 16-bit -->
    <tr>
      <td><code>short</code></td>
      <td><code>short_</code></td>
      <td><code>short</code></td>
    </tr>
    <tr>
      <td><code>unsignedShort</code></td>
      <td><code>unsigned_short</code></td>
      <td><code>unsigned&nbsp;short</code></td>
    </tr>

    <!-- 32-bit -->
    <tr>
      <td><code>int</code></td>
      <td><code>int_</code></td>
      <td><code>int</code></td>
    </tr>
    <tr>
      <td><code>unsignedInt</code></td>
      <td><code>unsigned_int</code></td>
      <td><code>unsigned&nbsp;int</code></td>
    </tr>

    <!-- 64-bit -->
    <tr>
      <td><code>long</code></td>
      <td><code>long_</code></td>
      <td><code>long&nbsp;long</code></td>
    </tr>
    <tr>
      <td><code>unsignedLong</code></td>
      <td><code>unsigned_long</code></td>
      <td><code>unsigned&nbsp;long&nbsp;long</code></td>
    </tr>

    <tr>
      <th colspan="3">arbitrary-length integral types</th>
    </tr>
    <tr>
      <td><code>integer</code></td>
      <td><code>integer</code></td>
      <td><code>long&nbsp;long</code></td>
    </tr>
    <tr>
      <td><code>nonPositiveInteger</code></td>
      <td><code>non_positive_integer</code></td>
      <td><code>long&nbsp;long</code></td>
    </tr>
    <tr>
      <td><code>nonNegativeInteger</code></td>
      <td><code>non_negative_integer</code></td>
      <td><code>unsigned long&nbsp;long</code></td>
    </tr>
    <tr>
      <td><code>positiveInteger</code></td>
      <td><code>positive_integer</code></td>
      <td><code>unsigned long&nbsp;long</code></td>
    </tr>
    <tr>
      <td><code>negativeInteger</code></td>
      <td><code>negative_integer</code></td>
      <td><code>long&nbsp;long</code></td>
    </tr>

    <tr>
      <th colspan="3">boolean types</th>
    </tr>
    <tr>
      <td><code>boolean</code></td>
      <td><code>boolean</code></td>
      <td><code>bool</code></td>
    </tr>

    <tr>
      <th colspan="3">fixed-precision floating-point types</th>
    </tr>
    <tr>
      <td><code>float</code></td>
      <td><code>float_</code></td>
      <td><code>float</code></td>
    </tr>
    <tr>
      <td><code>double</code></td>
      <td><code>double_</code></td>
      <td><code>double</code></td>
    </tr>

    <tr>
      <th colspan="3">arbitrary-precision floating-point types</th>
    </tr>
    <tr>
      <td><code>decimal</code></td>
      <td><code>decimal</code></td>
      <td><code>double</code></td>
    </tr>

    <tr>
      <th colspan="3">string types</th>
    </tr>
    <tr>
      <td><code>string</code></td>
      <td><code>string</code></td>
      <td>type derived from <code>std::basic_string</code></td>
    </tr>
    <tr>
      <td><code>normalizedString</code></td>
      <td><code>normalized_string</code></td>
      <td>type derived from <code>string</code></td>
    </tr>
    <tr>
      <td><code>token</code></td>
      <td><code>token</code></td>
      <td>type&nbsp;derived&nbsp;from&nbsp;<code>normalized_string</code></td>
    </tr>
    <tr>
      <td><code>Name</code></td>
      <td><code>name</code></td>
      <td>type derived from <code>token</code></td>
    </tr>
    <tr>
      <td><code>NMTOKEN</code></td>
      <td><code>nmtoken</code></td>
      <td>type derived from <code>token</code></td>
    </tr>
    <tr>
      <td><code>NMTOKENS</code></td>
      <td><code>nmtokens</code></td>
      <td>type derived from <code>sequence&lt;nmtoken></code></td>
    </tr>
    <tr>
      <td><code>NCName</code></td>
      <td><code>ncname</code></td>
      <td>type derived from <code>name</code></td>
    </tr>
    <tr>
      <td><code>language</code></td>
      <td><code>language</code></td>
      <td>type derived from <code>token</code></td>
    </tr>

    <tr>
      <th colspan="3">qualified name</th>
    </tr>
    <tr>
      <td><code>QName</code></td>
      <td><code>qname</code></td>
      <td><a href="#2.5.4">Section 2.5.4, "Mapping for <code>QName</code>"</a></td>
    </tr>

    <tr>
      <th colspan="3">ID/IDREF types</th>
    </tr>
    <tr>
      <td><code>ID</code></td>
      <td><code>id</code></td>
      <td>type derived from <code>ncname</code></td>
    </tr>
    <tr>
      <td><code>IDREF</code></td>
      <td><code>idref</code></td>
      <td><a href="#2.5.5">Section 2.5.5, "Mapping for <code>IDREF</code>"</a></td>
    </tr>
    <tr>
      <td><code>IDREFS</code></td>
      <td><code>idrefs</code></td>
      <td>type derived from <code>sequence&lt;idref></code></td>
    </tr>

    <tr>
      <th colspan="3">URI types</th>
    </tr>
    <tr>
      <td><code>anyURI</code></td>
      <td><code>uri</code></td>
      <td>type derived from <code>std::basic_string</code></td>
    </tr>

    <tr>
      <th colspan="3">binary types</th>
    </tr>
    <tr>
      <td><code>base64Binary</code></td>
      <td><code>base64_binary</code></td>
      <td rowspan="2"><a href="#2.5.6">Section 2.5.6, "Mapping for
         <code>base64Binary</code> and <code>hexBinary</code>"</a></td>
    </tr>
    <tr>
      <td><code>hexBinary</code></td>
      <td><code>hex_binary</code></td>
    </tr>

    <tr>
      <th colspan="3">date/time types</th>
    </tr>
    <tr>
      <td><code>date</code></td>
      <td><code>date</code></td>
      <td><a href="#2.5.8">Section 2.5.8, "Mapping for
          <code>date</code>"</a></td>
    </tr>
    <tr>
      <td><code>dateTime</code></td>
      <td><code>date_time</code></td>
      <td><a href="#2.5.9">Section 2.5.9, "Mapping for
          <code>dateTime</code>"</a></td>
    </tr>
    <tr>
      <td><code>duration</code></td>
      <td><code>duration</code></td>
      <td><a href="#2.5.10">Section 2.5.10, "Mapping for
          <code>duration</code>"</a></td>
    </tr>
    <tr>
      <td><code>gDay</code></td>
      <td><code>gday</code></td>
      <td><a href="#2.5.11">Section 2.5.11, "Mapping for
          <code>gDay</code>"</a></td>
    </tr>
    <tr>
      <td><code>gMonth</code></td>
      <td><code>gmonth</code></td>
      <td><a href="#2.5.12">Section 2.5.12, "Mapping for
          <code>gMonth</code>"</a></td>
    </tr>
    <tr>
      <td><code>gMonthDay</code></td>
      <td><code>gmonth_day</code></td>
      <td><a href="#2.5.13">Section 2.5.13, "Mapping for
          <code>gMonthDay</code>"</a></td>
    </tr>
    <tr>
      <td><code>gYear</code></td>
      <td><code>gyear</code></td>
      <td><a href="#2.5.14">Section 2.5.14, "Mapping for
          <code>gYear</code>"</a></td>
    </tr>
    <tr>
      <td><code>gYearMonth</code></td>
      <td><code>gyear_month</code></td>
      <td><a href="#2.5.15">Section 2.5.15, "Mapping for
          <code>gYearMonth</code>"</a></td>
    </tr>
    <tr>
      <td><code>time</code></td>
      <td><code>time</code></td>
      <td><a href="#2.5.16">Section 2.5.16, "Mapping for
          <code>time</code>"</a></td>
    </tr>

    <tr>
      <th colspan="3">entity types</th>
    </tr>
    <tr>
      <td><code>ENTITY</code></td>
      <td><code>entity</code></td>
      <td>type derived from <code>name</code></td>
    </tr>
    <tr>
      <td><code>ENTITIES</code></td>
      <td><code>entities</code></td>
      <td>type derived from <code>sequence&lt;entity></code></td>
    </tr>
  </table>

  <p>All XML Schema built-in types are mapped to C++ classes that are
     derived from the <code>xml_schema::simple_type</code> class except
     where the mapping is to a fundamental C++ type.</p>

  <p>The <code>sequence</code> class template is defined in an
     implementation-specific namespace. It conforms to the
     sequence interface as defined by the ISO/ANSI Standard for
     C++ (ISO/IEC 14882:1998, Section 23.1.1, "Sequences").
     Practically, this means that you can treat such a sequence
     as if it was <code>std::vector</code>. One notable extension
     to the standard interface that is available only for
     sequences of non-fundamental C++ types is the addition of
     the overloaded <code>push_back</code> and <code>insert</code>
     member functions which instead of the constant reference
     to the element type accept automatic pointer (<code>std::auto_ptr</code>
     or <code>std::unique_ptr</code>, depending on the C++ standard
     selected) to the element type. These functions assume ownership
     of the pointed to object and reset the passed automatic pointer.
  </p>

  <h3><a name="2.5.1">2.5.1 Inheritance from Built-in Data Types</a></h3>

  <p>In cases where the mapping calls for an inheritance from a built-in
     type which is mapped to a fundamental C++ type, a proxy type is
     used instead of the fundamental C++ type (C++ does not allow
     inheritance from fundamental types). For instance:</p>

  <pre class="xml">
&lt;simpleType name="my_int">
  &lt;restriction base="int"/>
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class my_int: public fundamental_base&lt;int>
{
  ...
};
  </pre>

  <p>The <code>fundamental_base</code> class template provides a close
     emulation (though not exact) of a fundamental C++ type.
     It is defined in an implementation-specific namespace and has the
     following interface:</p>

  <pre class="c++">
template &lt;typename X>
class fundamental_base: public simple_type
{
public:
  fundamental_base ();
  fundamental_base (X)
  fundamental_base (const fundamental_base&amp;)

public:
  fundamental_base&amp;
  operator= (const X&amp;);

public:
  operator const X &amp; () const;
  operator X&amp; ();

  template &lt;typename Y>
  operator Y () const;

  template &lt;typename Y>
  operator Y ();
};
  </pre>

  <h3><a name="2.5.2">2.5.2 Mapping for <code>anyType</code></a></h3>

  <p>The XML Schema <code>anyType</code> built-in data type is mapped to the
     <code>xml_schema::type</code> C++ class:</p>

  <pre class="c++">
class type
{
public:
  virtual
  ~type ();

  type ();
  type (const type&amp;);

  type&amp;
  operator= (const type&amp;);

  virtual type*
  _clone () const;

  // anyType DOM content.
  //
public:
  typedef element_optional dom_content_optional;

  const dom_content_optional&amp;
  dom_content () const;

  dom_content_optional&amp;
  dom_content ();

  void
  dom_content (const xercesc::DOMElement&amp;);

  void
  dom_content (xercesc::DOMElement*);

  void
  dom_content (const dom_content_optional&amp;);

  const xercesc::DOMDocument&amp;
  dom_content_document () const;

  xercesc::DOMDocument&amp;
  dom_content_document ();

  bool
  null_content () const;

  // DOM association.
  //
public:
  const xercesc::DOMNode*
  _node () const;

  xercesc::DOMNode*
  _node ();
};
  </pre>

  <p>When <code>xml_schema::type</code> is used to create an instance
     (as opposed to being a base of a derived type), it represents
     the XML Schema <code>anyType</code> type. <code>anyType</code>
     allows any attributes and any content in any order. In the
     C++/Tree mapping this content can be represented as a DOM
     fragment, similar to XML Schema wildcards (<a href="#2.12">Section
     2.12, "Mapping for <code>any</code> and
     <code>anyAttribute</code>"</a>).</p>

  <p>To enable automatic extraction of <code>anyType</code> content
     during parsing, the <code>--generate-any-type</code> option must be
     specified. Because the DOM API is used to access such content, the
     Xerces-C++ runtime should be initialized by the application prior to
     parsing and should remain initialized for the lifetime of objects
     with the DOM content. For more information on the Xerces-C++ runtime
     initialization see <a href="#3.1">Section 3.1, "Initializing the
     Xerces-C++ Runtime"</a>.</p>

  <p>The DOM content is stored as the optional DOM element container
     and the DOM content accessors and modifiers presented above are
     identical to those generated for an optional element wildcard.
     Refer to <a href="#2.12.2">Section 2.12.2, "Mapping for <code>any</code>
     with the Optional Cardinality Class"</a> for details on their
     semantics.</p>

  <p>The <code>dom_content_document()</code> function returns the
     DOM document used to store the raw XML content corresponding
     to the <code>anyType</code> instance. It is equivalent to the
     <code>dom_document()</code> function generated for types
     with wildcards.</p>

  <p>The <code>null_content()</code> accessor is an optimization function
     that allows us to check for the lack of content without actually
     creating its empty representation, that is, empty DOM document for
     <code>anyType</code> or empty string for <code>anySimpleType</code>
     (see the following section for details on <code>anySimpleType</code>).</p>

  <p>For more information on DOM association refer to
     <a href="#5.1">Section 5.1, "DOM Association"</a>.</p>

  <h3><a name="2.5.3">2.5.3 Mapping for <code>anySimpleType</code></a></h3>

  <p>The XML Schema <code>anySimpleType</code> built-in data type is mapped
     to the <code>xml_schema::simple_type</code> C++ class:</p>

  <pre class="c++">
class simple_type: public type
{
public:
  simple_type ();
  simple_type (const C*);
  simple_type (const std::basic_string&lt;C>&amp;);

  simple_type (const simple_type&amp;);

  simple_type&amp;
  operator= (const simple_type&amp;);

  virtual simple_type*
  _clone () const;

  // anySimpleType text content.
  //
public:
  const std::basic_string&lt;C>&amp;
  text_content () const;

  std::basic_string&lt;C>&amp;
  text_content ();

  void
  text_content (const std::basic_string&lt;C>&amp;);
};
  </pre>

  <p>When <code>xml_schema::simple_type</code> is used to create an instance
     (as opposed to being a base of a derived type), it represents
     the XML Schema <code>anySimpleType</code> type. <code>anySimpleType</code>
     allows any simple content. In the C++/Tree mapping this content can
     be represented as a string and accessed or modified with the
     <code>text_content()</code> functions shown above.</p>

  <h3><a name="2.5.4">2.5.4 Mapping for <code>QName</code></a></h3>

  <p>The XML Schema <code>QName</code> built-in data type is mapped to the
     <code>xml_schema::qname</code> C++ class:</p>

  <pre class="c++">
class qname: public simple_type
{
public:
  qname (const ncname&amp;);
  qname (const uri&amp;, const ncname&amp;);
  qname (const qname&amp;);

public:
  qname&amp;
  operator= (const qname&amp;);

public:
  virtual qname*
  _clone () const;

public:
  bool
  qualified () const;

  const uri&amp;
  namespace_ () const;

  const ncname&amp;
  name () const;
};
  </pre>

  <p>The <code>qualified</code> accessor function can be used to determine
     if the name is qualified.</p>

  <h3><a name="2.5.5">2.5.5 Mapping for <code>IDREF</code></a></h3>

  <p>The XML Schema <code>IDREF</code> built-in data type is mapped to the
     <code>xml_schema::idref</code> C++ class. This class implements the
     smart pointer C++ idiom:</p>

  <pre class="c++">
class idref: public ncname
{
public:
  idref (const C* s);
  idref (const C* s, std::size_t n);
  idref (std::size_t n, C c);
  idref (const std::basic_string&lt;C>&amp;);
  idref (const std::basic_string&lt;C>&amp;,
         std::size_t pos,
         std::size_t n = npos);

public:
  idref (const idref&amp;);

public:
  virtual idref*
  _clone () const;

public:
  idref&amp;
  operator= (C c);

  idref&amp;
  operator= (const C* s);

  idref&amp;
  operator= (const std::basic_string&lt;C>&amp;)

  idref&amp;
  operator= (const idref&amp;);

public:
  const type*
  operator-> () const;

  type*
  operator-> ();

  const type&amp;
  operator* () const;

  type&amp;
  operator* ();

  const type*
  get () const;

  type*
  get ();

  // Conversion to bool.
  //
public:
  typedef void (idref::*bool_convertible)();
  operator bool_convertible () const;
};
  </pre>

  <p>The object, <code>idref</code> instance refers to, is the immediate
     container of the matching <code>id</code> instance. For example,
     with the following instance document and schema:
  </p>


  <pre class="xml">
&lt;!-- test.xml -->
&lt;root>
  &lt;object id="obj-1" text="hello"/>
  &lt;reference>obj-1&lt;/reference>
&lt;/root>

&lt;!-- test.xsd -->
&lt;schema>
  &lt;complexType name="object_type">
    &lt;attribute name="id" type="ID"/>
    &lt;attribute name="text" type="string"/>
  &lt;/complexType>

  &lt;complexType name="root_type">
    &lt;sequence>
      &lt;element name="object" type="object_type"/>
      &lt;element name="reference" type="IDREF"/>
    &lt;/sequence>
  &lt;/complexType>

  &lt;element name="root" type="root_type"/>
&lt;/schema>
  </pre>

  <p>The <code>ref</code> instance in the code below will refer to
     an object of type <code>object_type</code>:</p>

  <pre class="c++">
root_type&amp; root = ...;
xml_schema::idref&amp; ref (root.reference ());
object_type&amp; obj (dynamic_cast&lt;object_type&amp;> (*ref));
cout &lt;&lt; obj.text () &lt;&lt; endl;
  </pre>

  <p>The smart pointer interface of the <code>idref</code> class always
     returns a pointer or reference to <code>xml_schema::type</code>.
     This means that you will need to manually cast such pointer or
     reference to its real (dynamic) type before you can use it (unless
     all you need is the base interface provided by
     <code>xml_schema::type</code>). As a special extension to the XML
     Schema language, the mapping supports static typing of <code>idref</code>
     references by employing the <code>refType</code> extension attribute.
     The following example illustrates this mechanism:
  </p>

  <pre class="xml">
&lt;!-- test.xsd -->
&lt;schema
  xmlns:xse="https://www.codesynthesis.com/xmlns/xml-schema-extension">

  ...

      &lt;element name="reference" type="IDREF" xse:refType="object_type"/>

  ...

&lt;/schema>
  </pre>

  <p>With this modification we do not need to do manual casting anymore:
  </p>

  <pre class="c++">
root_type&amp; root = ...;
root_type::reference_type&amp; ref (root.reference ());
object_type&amp; obj (*ref);
cout &lt;&lt; ref->text () &lt;&lt; endl;
  </pre>


  <h3><a name="2.5.6">2.5.6 Mapping for <code>base64Binary</code> and
      <code>hexBinary</code></a></h3>

  <p>The XML Schema <code>base64Binary</code> and <code>hexBinary</code>
     built-in data types are mapped to the
     <code>xml_schema::base64_binary</code> and
     <code>xml_schema::hex_binary</code> C++ classes, respectively. The
     <code>base64_binary</code> and <code>hex_binary</code> classes
     support a simple buffer abstraction by inheriting from the
     <code>xml_schema::buffer</code> class:
  </p>

  <pre class="c++">
class bounds: public virtual exception
{
public:
  virtual const char*
  what () const throw ();
};

class buffer
{
public:
  typedef std::size_t size_t;

public:
  buffer (size_t size = 0);
  buffer (size_t size, size_t capacity);
  buffer (const void* data, size_t size);
  buffer (const void* data, size_t size, size_t capacity);
  buffer (void* data,
          size_t size,
          size_t capacity,
          bool assume_ownership);

public:
  buffer (const buffer&amp;);

  buffer&amp;
  operator= (const buffer&amp;);

  void
  swap (buffer&amp;);

public:
  size_t
  capacity () const;

  bool
  capacity (size_t);

public:
  size_t
  size () const;

  bool
  size (size_t);

public:
  const char*
  data () const;

  char*
  data ();

  const char*
  begin () const;

  char*
  begin ();

  const char*
  end () const;

  char*
  end ();
};
  </pre>

  <p>The last overloaded constructor reuses an existing data buffer instead
     of making a copy. If the <code>assume_ownership</code> argument is
     <code>true</code>, the instance assumes ownership of the
     memory block pointed to by the <code>data</code> argument and will
     eventually release it by calling <code>operator delete</code>. The
     <code>capacity</code> and <code>size</code> modifier functions return
     <code>true</code> if the underlying buffer has moved.
  </p>

  <p>The <code>bounds</code> exception is thrown if the constructor
     arguments violate the <code>(size&nbsp;&lt;=&nbsp;capacity)</code>
     constraint.</p>

  <p>The <code>base64_binary</code> and <code>hex_binary</code> classes
     support the <code>buffer</code> interface and perform automatic
     decoding/encoding from/to the Base64 and Hex formats, respectively:
  </p>

  <pre class="c++">
class base64_binary: public simple_type, public buffer
{
public:
  base64_binary (size_t size = 0);
  base64_binary (size_t size, size_t capacity);
  base64_binary (const void* data, size_t size);
  base64_binary (const void* data, size_t size, size_t capacity);
  base64_binary (void* data,
                 size_t size,
                 size_t capacity,
                 bool assume_ownership);

public:
  base64_binary (const base64_binary&amp;);

  base64_binary&amp;
  operator= (const base64_binary&amp;);

  virtual base64_binary*
  _clone () const;

public:
  std::basic_string&lt;C>
  encode () const;
};
  </pre>

  <pre class="c++">
class hex_binary: public simple_type, public buffer
{
public:
  hex_binary (size_t size = 0);
  hex_binary (size_t size, size_t capacity);
  hex_binary (const void* data, size_t size);
  hex_binary (const void* data, size_t size, size_t capacity);
  hex_binary (void* data,
              size_t size,
              size_t capacity,
              bool assume_ownership);

public:
  hex_binary (const hex_binary&amp;);

  hex_binary&amp;
  operator= (const hex_binary&amp;);

  virtual hex_binary*
  _clone () const;

public:
  std::basic_string&lt;C>
  encode () const;
};
  </pre>


  <h2><a name="2.5.7">2.5.7 Time Zone Representation</a></h2>

  <p>The <code>date</code>, <code>dateTime</code>, <code>gDay</code>,
     <code>gMonth</code>, <code>gMonthDay</code>, <code>gYear</code>,
     <code>gYearMonth</code>, and <code>time</code> XML Schema built-in
     types all include an optional time zone component. The following
     <code>xml_schema::time_zone</code> base class is used to represent
     this information:</p>

  <pre class="c++">
class time_zone
{
public:
  time_zone ();
  time_zone (short hours, short minutes);

  bool
  zone_present () const;

  void
  zone_reset ();

  short
  zone_hours () const;

  void
  zone_hours (short);

  short
  zone_minutes () const;

  void
  zone_minutes (short);
};

bool
operator== (const time_zone&amp;, const time_zone&amp;);

bool
operator!= (const time_zone&amp;, const time_zone&amp;);
  </pre>

  <p>The <code>zone_present()</code> accessor function returns <code>true</code>
     if the time zone is specified. The <code>zone_reset()</code> modifier
     function resets the time zone object to the <em>not specified</em>
     state. If the time zone offset is negative then both hours and
     minutes components are represented as negative integers.</p>


  <h2><a name="2.5.8">2.5.8 Mapping for <code>date</code></a></h2>

 <p>The XML Schema <code>date</code> built-in data type is mapped to the
    <code>xml_schema::date</code> C++ class which represents a year, a day,
    and a month with an optional time zone. Its interface is presented
    below. For more information on the base <code>xml_schema::time_zone</code>
    class refer to <a href="#2.5.7">Section 2.5.7, "Time Zone
    Representation"</a>.</p>

  <pre class="c++">
class date: public simple_type, public time_zone
{
public:
  date (int year, unsigned short month, unsigned short day);
  date (int year, unsigned short month, unsigned short day,
        short zone_hours, short zone_minutes);

public:
  date (const date&amp;);

  date&amp;
  operator= (const date&amp;);

  virtual date*
  _clone () const;

public:
  int
  year () const;

  void
  year (int);

  unsigned short
  month () const;

  void
  month (unsigned short);

  unsigned short
  day () const;

  void
  day (unsigned short);
};

bool
operator== (const date&amp;, const date&amp;);

bool
operator!= (const date&amp;, const date&amp;);
  </pre>

  <h2><a name="2.5.9">2.5.9 Mapping for <code>dateTime</code></a></h2>

 <p>The XML Schema <code>dateTime</code> built-in data type is mapped to the
    <code>xml_schema::date_time</code> C++ class which represents a year, a month,
    a day, hours, minutes, and seconds with an optional time zone. Its interface
    is presented below. For more information on the base
    <code>xml_schema::time_zone</code> class refer to <a href="#2.5.7">Section
    2.5.7, "Time Zone Representation"</a>.</p>

  <pre class="c++">
class date_time: public simple_type, public time_zone
{
public:
  date_time (int year, unsigned short month, unsigned short day,
             unsigned short hours, unsigned short minutes,
             double seconds);

  date_time (int year, unsigned short month, unsigned short day,
             unsigned short hours, unsigned short minutes,
             double seconds, short zone_hours, short zone_minutes);
public:
  date_time (const date_time&amp;);

  date_time&amp;
  operator= (const date_time&amp;);

  virtual date_time*
  _clone () const;

public:
  int
  year () const;

  void
  year (int);

  unsigned short
  month () const;

  void
  month (unsigned short);

  unsigned short
  day () const;

  void
  day (unsigned short);

  unsigned short
  hours () const;

  void
  hours (unsigned short);

  unsigned short
  minutes () const;

  void
  minutes (unsigned short);

  double
  seconds () const;

  void
  seconds (double);
};

bool
operator== (const date_time&amp;, const date_time&amp;);

bool
operator!= (const date_time&amp;, const date_time&amp;);
  </pre>


  <h2><a name="2.5.10">2.5.10 Mapping for <code>duration</code></a></h2>

  <p>The XML Schema <code>duration</code> built-in data type is mapped to the
    <code>xml_schema::duration</code> C++ class which represents a potentially
     negative duration in the form of years, months, days, hours, minutes,
     and seconds. Its interface is presented below.</p>

  <pre class="c++">
class duration: public simple_type
{
public:
  duration (bool negative,
            unsigned int years, unsigned int months, unsigned int days,
            unsigned int hours, unsigned int minutes, double seconds);
public:
  duration (const duration&amp;);

  duration&amp;
  operator= (const duration&amp;);

  virtual duration*
  _clone () const;

public:
  bool
  negative () const;

  void
  negative (bool);

  unsigned int
  years () const;

  void
  years (unsigned int);

  unsigned int
  months () const;

  void
  months (unsigned int);

  unsigned int
  days () const;

  void
  days (unsigned int);

  unsigned int
  hours () const;

  void
  hours (unsigned int);

  unsigned int
  minutes () const;

  void
  minutes (unsigned int);

  double
  seconds () const;

  void
  seconds (double);
};

bool
operator== (const duration&amp;, const duration&amp;);

bool
operator!= (const duration&amp;, const duration&amp;);
  </pre>


  <h2><a name="2.5.11">2.5.11 Mapping for <code>gDay</code></a></h2>

  <p>The XML Schema <code>gDay</code> built-in data type is mapped to the
    <code>xml_schema::gday</code> C++ class which represents a day of the
     month with an optional time zone. Its interface is presented below.
     For more information on the base <code>xml_schema::time_zone</code>
     class refer to <a href="#2.5.7">Section 2.5.7, "Time Zone
     Representation"</a>.</p>

  <pre class="c++">
class gday: public simple_type, public time_zone
{
public:
  explicit
  gday (unsigned short day);
  gday (unsigned short day, short zone_hours, short zone_minutes);

public:
  gday (const gday&amp;);

  gday&amp;
  operator= (const gday&amp;);

  virtual gday*
  _clone () const;

public:
  unsigned short
  day () const;

  void
  day (unsigned short);
};

bool
operator== (const gday&amp;, const gday&amp;);

bool
operator!= (const gday&amp;, const gday&amp;);
  </pre>


  <h2><a name="2.5.12">2.5.12 Mapping for <code>gMonth</code></a></h2>

  <p>The XML Schema <code>gMonth</code> built-in data type is mapped to the
    <code>xml_schema::gmonth</code> C++ class which represents a month of the
     year with an optional time zone. Its interface is presented below.
     For more information on the base <code>xml_schema::time_zone</code>
     class refer to <a href="#2.5.7">Section 2.5.7, "Time Zone
     Representation"</a>.</p>

  <pre class="c++">
class gmonth: public simple_type, public time_zone
{
public:
  explicit
  gmonth (unsigned short month);
  gmonth (unsigned short month,
          short zone_hours, short zone_minutes);

public:
  gmonth (const gmonth&amp;);

  gmonth&amp;
  operator= (const gmonth&amp;);

  virtual gmonth*
  _clone () const;

public:
  unsigned short
  month () const;

  void
  month (unsigned short);
};

bool
operator== (const gmonth&amp;, const gmonth&amp;);

bool
operator!= (const gmonth&amp;, const gmonth&amp;);
  </pre>


  <h2><a name="2.5.13">2.5.13 Mapping for <code>gMonthDay</code></a></h2>

  <p>The XML Schema <code>gMonthDay</code> built-in data type is mapped to the
    <code>xml_schema::gmonth_day</code> C++ class which represents a day and
     a month of the year with an optional time zone. Its interface is presented
     below. For more information on the base <code>xml_schema::time_zone</code>
     class refer to <a href="#2.5.7">Section 2.5.7, "Time Zone
     Representation"</a>.</p>

  <pre class="c++">
class gmonth_day: public simple_type, public time_zone
{
public:
  gmonth_day (unsigned short month, unsigned short day);
  gmonth_day (unsigned short month, unsigned short day,
              short zone_hours, short zone_minutes);

public:
  gmonth_day (const gmonth_day&amp;);

  gmonth_day&amp;
  operator= (const gmonth_day&amp;);

  virtual gmonth_day*
  _clone () const;

public:
  unsigned short
  month () const;

  void
  month (unsigned short);

  unsigned short
  day () const;

  void
  day (unsigned short);
};

bool
operator== (const gmonth_day&amp;, const gmonth_day&amp;);

bool
operator!= (const gmonth_day&amp;, const gmonth_day&amp;);
  </pre>


  <h2><a name="2.5.14">2.5.14 Mapping for <code>gYear</code></a></h2>

  <p>The XML Schema <code>gYear</code> built-in data type is mapped to the
    <code>xml_schema::gyear</code> C++ class which represents a year with
     an optional time zone. Its interface is presented below. For more
     information on the base <code>xml_schema::time_zone</code> class refer
     to <a href="#2.5.7">Section 2.5.7, "Time Zone Representation"</a>.</p>

  <pre class="c++">
class gyear: public simple_type, public time_zone
{
public:
  explicit
  gyear (int year);
  gyear (int year, short zone_hours, short zone_minutes);

public:
  gyear (const gyear&amp;);

  gyear&amp;
  operator= (const gyear&amp;);

  virtual gyear*
  _clone () const;

public:
  int
  year () const;

  void
  year (int);
};

bool
operator== (const gyear&amp;, const gyear&amp;);

bool
operator!= (const gyear&amp;, const gyear&amp;);
  </pre>


  <h2><a name="2.5.15">2.5.15 Mapping for <code>gYearMonth</code></a></h2>

  <p>The XML Schema <code>gYearMonth</code> built-in data type is mapped to
     the <code>xml_schema::gyear_month</code> C++ class which represents
     a year and a month with an optional time zone. Its interface is presented
     below. For more information on the base <code>xml_schema::time_zone</code>
     class refer to <a href="#2.5.7">Section 2.5.7, "Time Zone
     Representation"</a>.</p>

  <pre class="c++">
class gyear_month: public simple_type, public time_zone
{
public:
  gyear_month (int year, unsigned short month);
  gyear_month (int year, unsigned short month,
               short zone_hours, short zone_minutes);
public:
  gyear_month (const gyear_month&amp;);

  gyear_month&amp;
  operator= (const gyear_month&amp;);

  virtual gyear_month*
  _clone () const;

public:
  int
  year () const;

  void
  year (int);

  unsigned short
  month () const;

  void
  month (unsigned short);
};

bool
operator== (const gyear_month&amp;, const gyear_month&amp;);

bool
operator!= (const gyear_month&amp;, const gyear_month&amp;);
  </pre>


  <h2><a name="2.5.16">2.5.16 Mapping for <code>time</code></a></h2>

  <p>The XML Schema <code>time</code> built-in data type is mapped to
     the <code>xml_schema::time</code> C++ class which represents hours,
     minutes, and seconds with an optional time zone. Its interface is
     presented below. For more information on the base
     <code>xml_schema::time_zone</code> class refer to
     <a href="#2.5.7">Section 2.5.7, "Time Zone Representation"</a>.</p>

  <pre class="c++">
class time: public simple_type, public time_zone
{
public:
  time (unsigned short hours, unsigned short minutes, double seconds);
  time (unsigned short hours, unsigned short minutes, double seconds,
        short zone_hours, short zone_minutes);

public:
  time (const time&amp;);

  time&amp;
  operator= (const time&amp;);

  virtual time*
  _clone () const;

public:
  unsigned short
  hours () const;

  void
  hours (unsigned short);

  unsigned short
  minutes () const;

  void
  minutes (unsigned short);

  double
  seconds () const;

  void
  seconds (double);
};

bool
operator== (const time&amp;, const time&amp;);

bool
operator!= (const time&amp;, const time&amp;);
  </pre>


  <!-- Mapping for Simple Types -->

  <h2><a name="2.6">2.6 Mapping for Simple Types</a></h2>

  <p>An XML Schema simple type is mapped to a C++ class with the same
     name as the simple type. The class defines a public copy constructor,
     a public copy assignment operator, and a public virtual
     <code>_clone</code> function. The <code>_clone</code> function is
     declared <code>const</code>, does not take any arguments, and returns
     a pointer to a complete copy of the instance allocated in the free
     store. The <code>_clone</code> function shall be used to make copies
     when static type and dynamic type of the instance may differ (see
     <a href="#2.11">Section 2.11, "Mapping for <code>xsi:type</code>
     and Substitution Groups"</a>). For instance:</p>

  <pre class="xml">
&lt;simpleType name="object">
  ...
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: ...
{
public:
  object (const object&amp;);

public:
  object&amp;
  operator= (const object&amp;);

public:
  virtual object*
  _clone () const;

  ...

};
  </pre>

  <p>The base class specification and the rest of the class definition
     depend on the type of derivation used to define the simple type. </p>


  <h3><a name="2.6.1">2.6.1 Mapping for Derivation by Restriction</a></h3>

  <p>XML Schema derivation by restriction is mapped to C++ public
     inheritance. The base type of the restriction becomes the base
     type for the resulting C++ class. In addition to the members described
     in <a href="#2.6">Section 2.6, "Mapping for Simple Types"</a>, the
     resulting C++ class defines a public constructor with the base type
     as its single argument. For instance:</p>

  <pre class="xml">
&lt;simpleType name="object">
  &lt;restriction base="base">
    ...
  &lt;/restriction>
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public base
{
public:
  object (const base&amp;);
  object (const object&amp;);

public:
  object&amp;
  operator= (const object&amp;);

public:
  virtual object*
  _clone () const;
};
  </pre>


  <h3><a name="2.6.2">2.6.2 Mapping for Enumerations</a></h3>

<p>XML Schema restriction by enumeration is mapped to a C++ class
   with semantics similar to C++ <code>enum</code>. Each XML Schema
   enumeration element is mapped to a C++ enumerator with the
   name derived from the <code>value</code> attribute and defined
   in the class scope. In addition to the members
   described in <a href="#2.6">Section 2.6, "Mapping for Simple Types"</a>,
   the resulting C++ class defines a public constructor that can be called
   with one of the enumerators as its single argument, a public constructor
   that can be called with enumeration's base value as its single
   argument, a public assignment operator that can be used to assign the
   value of one of the enumerators, and a public implicit conversion
   operator to the underlying C++ enum type.</p>

<p>Furthermore, for string-based enumeration types, the resulting C++
   class defines a public constructor with a single argument of type
   <code>const C*</code> and a public constructor with a single
   argument of type <code>const std::basic_string&lt;C>&amp;</code>.
   For instance:</p>

  <pre class="xml">
&lt;simpleType name="color">
  &lt;restriction base="string">
    &lt;enumeration value="red"/>
    &lt;enumeration value="green"/>
    &lt;enumeration value="blue"/>
  &lt;/restriction>
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class color: public xml_schema::string
{
public:
  enum value
  {
    red,
    green,
    blue
  };

public:
  color (value);
  color (const C*);
  color (const std::basic_string&lt;C>&amp;);
  color (const xml_schema::string&amp;);
  color (const color&amp;);

public:
  color&amp;
  operator= (value);

  color&amp;
  operator= (const color&amp;);

public:
  virtual color*
  _clone () const;

public:
  operator value () const;
};
  </pre>

  <h3><a name="2.6.3">2.6.3 Mapping for Derivation by List</a></h3>

  <p>XML Schema derivation by list is mapped to C++ public
     inheritance from <code>xml_schema::simple_type</code>
     (<a href="#2.5.3">Section 2.5.3, "Mapping for
     <code>anySimpleType</code>"</a>) and a suitable sequence type.
     The list item type becomes the element type of the sequence.
     In addition to the members described in <a href="#2.6">Section 2.6,
     "Mapping for Simple Types"</a>, the resulting C++ class defines
     a public default constructor, a public constructor
     with the first argument of type <code>size_type</code> and
     the second argument of list item type that creates
     a list object with the specified number of copies of the specified
     element value, and a public constructor with the two arguments
     of an input iterator type that creates a list object from an
     iterator range. For instance:
  </p>

  <pre class="xml">
&lt;simpleType name="int_list">
  &lt;list itemType="int"/>
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class int_list: public simple_type,
                public sequence&lt;int>
{
public:
  int_list ();
  int_list (size_type n, int x);

  template &lt;typename I>
  int_list (const I&amp; begin, const I&amp; end);
  int_list (const int_list&amp;);

public:
  int_list&amp;
  operator= (const int_list&amp;);

public:
  virtual int_list*
  _clone () const;
};
  </pre>

  <p>The <code>sequence</code> class template is defined in an
     implementation-specific namespace. It conforms to the
     sequence interface as defined by the ISO/ANSI Standard for
     C++ (ISO/IEC 14882:1998, Section 23.1.1, "Sequences").
     Practically, this means that you can treat such a sequence
     as if it was <code>std::vector</code>. One notable extension
     to the standard interface that is available only for
     sequences of non-fundamental C++ types is the addition of
     the overloaded <code>push_back</code> and <code>insert</code>
     member functions which instead of the constant reference
     to the element type accept automatic pointer (<code>std::auto_ptr</code>
     or <code>std::unique_ptr</code>, depending on the C++ standard
     selected) to the element type. These functions assume ownership
     of the pointed to object and reset the passed automatic pointer.
  </p>

  <h3><a name="2.6.4">2.6.4 Mapping for Derivation by Union</a></h3>

  <p>XML Schema derivation by union is mapped to C++ public
     inheritance from <code>xml_schema::simple_type</code>
     (<a href="#2.5.3">Section 2.5.3, "Mapping for
     <code>anySimpleType</code>"</a>) and <code>std::basic_string&lt;C></code>.
     In addition to the members described in <a href="#2.6">Section 2.6,
     "Mapping for Simple Types"</a>, the resulting C++ class defines a
     public constructor with a single argument of type <code>const C*</code>
     and a public constructor with a single argument of type
     <code>const std::basic_string&lt;C>&amp;</code>. For instance:
  </p>

  <pre class="xml">
&lt;simpleType name="int_string_union">
  &lt;xsd:union memberTypes="xsd:int xsd:string"/>
&lt;/simpleType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class int_string_union: public simple_type,
                        public std::basic_string&lt;C>
{
public:
  int_string_union (const C*);
  int_string_union (const std::basic_string&lt;C>&amp;);
  int_string_union (const int_string_union&amp;);

public:
  int_string_union&amp;
  operator= (const int_string_union&amp;);

public:
  virtual int_string_union*
  _clone () const;
};
  </pre>

  <h2><a name="2.7">2.7 Mapping for Complex Types</a></h2>

  <p>An XML Schema complex type is mapped to a C++ class with the same
     name as the complex type. The class defines a public copy constructor,
     a public copy assignment operator, and a public virtual
     <code>_clone</code> function. The <code>_clone</code> function is
     declared <code>const</code>, does not take any arguments, and returns
     a pointer to a complete copy of the instance allocated in the free
     store. The <code>_clone</code> function shall be used to make copies
     when static type and dynamic type of the instance may differ (see
     <a href="#2.11">Section 2.11, "Mapping for <code>xsi:type</code>
     and Substitution Groups"</a>).</p>

  <p>Additionally, the resulting C++ class
     defines two public constructors that take an initializer for each
     member of the complex type and all its base types that belongs to
     the One cardinality class (see <a href="#2.8">Section 2.8, "Mapping
     for Local Elements and Attributes"</a>). In the first constructor,
     the arguments are passed as constant references and the newly created
     instance is initialized with copies of the passed objects. In the
     second constructor, arguments that are complex types (that is,
     they themselves contain elements or attributes) are passed as
     either <code>std::auto_ptr</code> (C++98) or <code>std::unique_ptr</code>
     (C++11), depending on the C++ standard selected. In this case the newly
     created instance is directly initialized with and assumes ownership
     of the pointed to objects and the <code>std::[auto|unique]_ptr</code>
     arguments are reset to <code>0</code>. For instance:</p>

  <pre class="xml">
&lt;complexType name="complex">
  &lt;sequence>
    &lt;element name="a" type="int"/>
    &lt;element name="b" type="string"/>
  &lt;/sequence>
&lt;/complexType>

&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="s-one" type="boolean"/>
    &lt;element name="c-one" type="complex"/>
    &lt;element name="optional" type="int" minOccurs="0"/>
    &lt;element name="sequence" type="string" maxOccurs="unbounded"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class complex: public xml_schema::type
{
public:
  object (const int&amp; a, const xml_schema::string&amp; b);
  object (const complex&amp;);

public:
  object&amp;
  operator= (const complex&amp;);

public:
  virtual complex*
  _clone () const;

  ...

};

class object: public xml_schema::type
{
public:
  object (const bool&amp; s_one, const complex&amp; c_one);
  object (const bool&amp; s_one, std::[auto|unique]_ptr&lt;complex> c_one);
  object (const object&amp;);

public:
  object&amp;
  operator= (const object&amp;);

public:
  virtual object*
  _clone () const;

  ...

};
  </pre>

  <p>Notice that the generated <code>complex</code> class does not
     have the second (<code>std::[auto|unique]_ptr</code>) version of the
     constructor since all its required members are of simple types.</p>

  <p>If an XML Schema complex type has an ultimate base which is an XML
     Schema simple type then the resulting C++ class also defines a public
     constructor that takes an initializer for the base type as well as
     for each member of the complex type and all its base types that
     belongs to the One cardinality class. For instance:</p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;simpleContent>
    &lt;extension base="date">
      &lt;attribute name="lang" type="language" use="required"/>
    &lt;/extension>
  &lt;/simpleContent>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::string
{
public:
  object (const xml_schema::language&amp; lang);

  object (const xml_schema::date&amp; base,
          const xml_schema::language&amp; lang);

  ...

};
  </pre>

  <p>Furthermore, for string-based XML Schema complex types, the resulting C++
     class also defines two  public constructors with the first arguments
     of type <code>const C*</code> and <code>std::basic_string&lt;C>&amp;</code>,
     respectively, followed by arguments for each member of the complex
     type and all its base types that belongs to the One cardinality
     class. For enumeration-based complex types the resulting C++
     class also defines a public constructor with the first arguments
     of the underlying enum type followed by arguments for each member
     of the complex type and all its base types that belongs to the One
     cardinality class. For instance:</p>

  <pre class="xml">
&lt;simpleType name="color">
  &lt;restriction base="string">
    &lt;enumeration value="red"/>
    &lt;enumeration value="green"/>
    &lt;enumeration value="blue"/>
  &lt;/restriction>
&lt;/simpleType>

&lt;complexType name="object">
  &lt;simpleContent>
    &lt;extension base="color">
      &lt;attribute name="lang" type="language" use="required"/>
    &lt;/extension>
  &lt;/simpleContent>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class color: public xml_schema::string
{
public:
  enum value
  {
    red,
    green,
    blue
  };

public:
  color (value);
  color (const C*);
  color (const std::basic_string&lt;C>&amp;);

  ...

};

class object: color
{
public:
  object (const color&amp; base,
          const xml_schema::language&amp; lang);

  object (const color::value&amp; base,
          const xml_schema::language&amp; lang);

  object (const C* base,
          const xml_schema::language&amp; lang);

  object (const std::basic_string&lt;C>&amp; base,
          const xml_schema::language&amp; lang);

  ...

};
  </pre>

  <p>Additional constructors can be requested with the
     <code>--generate-default-ctor</code> and
     <code>--generate-from-base-ctor</code> options. See the
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a> for details.</p>

  <p>If an XML Schema complex type is not explicitly derived from any type,
     the resulting C++ class is derived from <code>xml_schema::type</code>.
     In cases where an XML Schema complex type is defined using derivation
     by extension or restriction, the resulting C++ base class specification
     depends on the type of derivation and is described in the subsequent
     sections.
  </p>

  <p>The mapping for elements and attributes that are defined in a complex
     type is described in <a href="#2.8">Section 2.8, "Mapping for Local
     Elements and Attributes"</a>.
  </p>

  <h3><a name="2.7.1">2.7.1 Mapping for Derivation by Extension</a></h3>

  <p>XML Schema derivation by extension is mapped to C++ public
     inheritance. The base type of the extension becomes the base
     type for the resulting C++ class.
  </p>

  <h3><a name="2.7.2">2.7.2 Mapping for Derivation by Restriction</a></h3>

  <p>XML Schema derivation by restriction is mapped to C++ public
     inheritance. The base type of the restriction becomes the base
     type for the resulting C++ class. XML Schema elements and
     attributes defined within restriction do not result in any
     definitions in the resulting C++ class. Instead, corresponding
     (unrestricted) definitions are inherited from the base class.
     In the future versions of this mapping, such elements and
     attributes may result in redefinitions of accessors and
     modifiers to reflect their restricted semantics.
  </p>

  <!-- 2.8 Mapping for Local Elements and Attributes -->

  <h2><a name="2.8">2.8 Mapping for Local Elements and Attributes</a></h2>

   <p>XML Schema element and attribute definitions are called local
      if they appear within a complex type definition, an element group
      definition, or an attribute group definitions.
   </p>

   <p>Local XML Schema element and attribute definitions have the same
      C++ mapping. Therefore, in this section, local elements and
      attributes are collectively called members.
   </p>

   <p>While there are many different member cardinality combinations
      (determined by the <code>use</code> attribute for attributes and
       the <code>minOccurs</code> and <code>maxOccurs</code> attributes
       for elements), the mapping divides all possible cardinality
       combinations into three cardinality classes:
   </p>

   <dl>
     <dt><i>one</i></dt>
     <dd>attributes: <code>use == "required"</code></dd>
     <dd>attributes: <code>use == "optional"</code> and has default or fixed value</dd>
     <dd>elements: <code>minOccurs == "1"</code> and <code>maxOccurs == "1"</code></dd>

     <dt><i>optional</i></dt>
     <dd>attributes: <code>use == "optional"</code> and doesn't have default or fixed value</dd>
     <dd>elements: <code>minOccurs == "0"</code> and <code>maxOccurs == "1"</code></dd>

     <dt><i>sequence</i></dt>
     <dd>elements: <code>maxOccurs > "1"</code></dd>
   </dl>

   <p>An optional attribute with a default or fixed value acquires this value
      if the attribute hasn't been specified in an instance document (see
      <a href="#A">Appendix A, "Default and Fixed Values"</a>). This
      mapping places such optional attributes to the One cardinality
      class.</p>

   <p>A member is mapped to a set of public type definitions
      (<code>typedef</code>s) and a set of public accessor and modifier
      functions. Type definitions have names derived from the member's
      name. The accessor and modifier functions have the same name as the
      member. For example:
   </p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="member" type="string"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  typedef xml_schema::string member_type;

  const member_type&amp;
  member () const;

  ...

};
  </pre>

   <p>In addition, if a member has a default or fixed value, a static
      accessor function is generated that returns this value. For
      example:</p>

<pre class="xml">
&lt;complexType name="object">
  &lt;attribute name="data" type="string" default="test"/>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  typedef xml_schema::string data_type;

  const data_type&amp;
  data () const;

  static const data_type&amp;
  data_default_value ();

  ...

};
  </pre>

   <p>Names and semantics of type definitions for the member as well
      as signatures of the accessor and modifier functions depend on
      the member's cardinality class and are described in the following
      sub-sections.
   </p>


  <h3><a name="2.8.1">2.8.1 Mapping for Members with the One Cardinality Class</a></h3>

   <p>For the One cardinality class, the type definitions consist of
      an alias for the member's type with the name created by appending
      the <code>_type</code> suffix to the member's name.
   </p>

   <p>The accessor functions come in constant and non-constant versions.
      The constant accessor function returns a constant reference to the
      member and can be used for read-only access. The non-constant
      version returns an unrestricted reference to the member and can
      be used for read-write access.
   </p>

   <p>The first modifier function expects an argument of type reference to
      constant of the member's type. It makes a deep copy of its argument.
      Except for member's types that are mapped to fundamental C++ types,
      the second modifier function is provided that expects an argument
      of type automatic pointer (<code>std::auto_ptr</code> or
      <code>std::unique_ptr</code>, depending on the C++ standard selected)
      to the member's type. It assumes ownership of the pointed to object
      and resets the passed automatic pointer. For instance:</p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="member" type="string"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef xml_schema::string member_type;

  // Accessors.
  //
  const member_type&amp;
  member () const;

  member_type&amp;
  member ();

  // Modifiers.
  //
  void
  member (const member_type&amp;);

  void
  member (std::[auto|unique]_ptr&lt;member_type>);
  ...

};
  </pre>

   <p>In addition, if requested by specifying the <code>--generate-detach</code>
      option and only for members of non-fundamental C++ types, the mapping
      provides a detach function that returns an automatic pointer to the
      member's type, for example:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  ...

  std::[auto|unique]_ptr&lt;member_type>
  detach_member ();
  ...

};
  </pre>

   <p>This function detaches the value from the tree leaving the member
      value uninitialized. Accessing such an uninitialized value prior to
      re-initializing it results in undefined behavior.</p>

  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o)
{
  using xml_schema::string;

  string s (o.member ());                // get
  object::member_type&amp; sr (o.member ()); // get

  o.member ("hello");           // set, deep copy
  o.member () = "hello";        // set, deep copy

  // C++98 version.
  //
  std::auto_ptr&lt;string> p (new string ("hello"));
  o.member (p);                 // set, assumes ownership
  p = o.detach_member ();       // detach, member is uninitialized
  o.member (p);                 // re-attach

  // C++11 version.
  //
  std::unique_ptr&lt;string> p (new string ("hello"));
  o.member (std::move (p));     // set, assumes ownership
  p = o.detach_member ();       // detach, member is uninitialized
  o.member (std::move (p));     // re-attach
}
  </pre>


<h3><a name="2.8.2">2.8.2 Mapping for Members with the Optional Cardinality Class</a></h3>

   <p>For the Optional cardinality class, the type definitions consist of
      an alias for the member's type with the name created by appending
      the <code>_type</code> suffix to the member's name and an alias for
      the container type with the name created by appending the
      <code>_optional</code> suffix to the member's name.
   </p>

   <p>Unlike accessor functions for the One cardinality class, accessor
      functions for the Optional cardinality class return references to
      corresponding containers rather than directly to members. The
      accessor functions come in constant and non-constant versions.
      The constant accessor function returns a constant reference to
      the container and can be used for read-only access. The non-constant
      version returns an unrestricted reference to the container
      and can be used for read-write access.
   </p>

   <p>The modifier functions are overloaded for the member's
      type and the container type. The first modifier function
      expects an argument of type reference to constant of the
      member's type. It makes a deep copy of its argument.
      Except for member's types that are mapped to fundamental C++ types,
      the second modifier function is provided that expects an argument
      of type automatic pointer (<code>std::auto_ptr</code> or
      <code>std::unique_ptr</code>, depending on the C++ standard selected)
      to the member's type. It assumes ownership of the pointed to object
      and resets the passed automatic pointer. The last modifier function
      expects an argument of type reference to constant of the container
      type. It makes a deep copy of its argument. For instance:
   </p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="member" type="string" minOccurs="0"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef xml_schema::string member_type;
  typedef optional&lt;member_type> member_optional;

  // Accessors.
  //
  const member_optional&amp;
  member () const;

  member_optional&amp;
  member ();

  // Modifiers.
  //
  void
  member (const member_type&amp;);

  void
  member (std::[auto|unique]_ptr&lt;member_type>);

  void
  member (const member_optional&amp;);

  ...

};
  </pre>


  <p>The <code>optional</code> class template is defined in an
     implementation-specific namespace and has the following
     interface. The <code>[auto|unique]_ptr</code>-based constructor
     and modifier function are only available if the template
     argument is not a fundamental C++ type.
  </p>

  <pre class="c++">
template &lt;typename X>
class optional
{
public:
  optional ();

  // Makes a deep copy.
  //
  explicit
  optional (const X&amp;);

  // Assumes ownership.
  //
  explicit
  optional (std::[auto|unique]_ptr&lt;X>);

  optional (const optional&amp;);

public:
  optional&amp;
  operator= (const X&amp;);

  optional&amp;
  operator= (const optional&amp;);

  // Pointer-like interface.
  //
public:
  const X*
  operator-> () const;

  X*
  operator-> ();

  const X&amp;
  operator* () const;

  X&amp;
  operator* ();

  typedef void (optional::*bool_convertible) ();
  operator bool_convertible () const;

  // Get/set interface.
  //
public:
  bool
  present () const;

  const X&amp;
  get () const;

  X&amp;
  get ();

  // Makes a deep copy.
  //
  void
  set (const X&amp;);

  // Assumes ownership.
  //
  void
  set (std::[auto|unique]_ptr&lt;X>);

  // Detach and return the contained value.
  //
  std::[auto|unique]_ptr&lt;X>
  detach ();

  void
  reset ();
};

template &lt;typename X>
bool
operator== (const optional&lt;X>&amp;, const optional&lt;X>&amp;);

template &lt;typename X>
bool
operator!= (const optional&lt;X>&amp;, const optional&lt;X>&amp;);

template &lt;typename X>
bool
operator&lt; (const optional&lt;X>&amp;, const optional&lt;X>&amp;);

template &lt;typename X>
bool
operator> (const optional&lt;X>&amp;, const optional&lt;X>&amp;);

template &lt;typename X>
bool
operator&lt;= (const optional&lt;X>&amp;, const optional&lt;X>&amp;);

template &lt;typename X>
bool
operator>= (const optional&lt;X>&amp;, const optional&lt;X>&amp;);
  </pre>


  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o)
{
  using xml_schema::string;

  if (o.member ().present ())       // test
  {
    string&amp; s (o.member ().get ()); // get
    o.member ("hello");             // set, deep copy
    o.member ().set ("hello");      // set, deep copy
    o.member ().reset ();           // reset
  }

  // Same as above but using pointer notation:
  //
  if (o.member ())                  // test
  {
    string&amp; s (*o.member ());       // get
    o.member ("hello");             // set, deep copy
    *o.member () = "hello";         // set, deep copy
    o.member ().reset ();           // reset
  }

  // C++98 version.
  //
  std::auto_ptr&lt;string> p (new string ("hello"));
  o.member (p);                     // set, assumes ownership

  p = new string ("hello");
  o.member ().set (p);              // set, assumes ownership

  p = o.member ().detach ();        // detach, member is reset
  o.member ().set (p);              // re-attach

  // C++11 version.
  //
  std::unique_ptr&lt;string> p (new string ("hello"));
  o.member (std::move (p));         // set, assumes ownership

  p.reset (new string ("hello"));
  o.member ().set (std::move (p));  // set, assumes ownership

  p = o.member ().detach ();        // detach, member is reset
  o.member ().set (std::move (p));  // re-attach
}
  </pre>


  <h3><a name="2.8.3">2.8.3 Mapping for Members with the Sequence Cardinality Class</a></h3>

   <p>For the Sequence cardinality class, the type definitions consist of an
      alias for the member's type with the name created by appending
      the <code>_type</code> suffix to the member's name, an alias of
      the container type with the name created by appending the
      <code>_sequence</code> suffix to the member's name, an alias of
      the iterator type with the name created by appending the
      <code>_iterator</code> suffix to the member's name, and an alias
      of the constant iterator type with the name created by appending the
      <code>_const_iterator</code> suffix to the member's name.
   </p>

   <p>The accessor functions come in constant and non-constant versions.
      The constant accessor function returns a constant reference to the
      container and can be used for read-only access. The non-constant
      version returns an unrestricted reference to the container and can
      be used for read-write access.
   </p>

   <p>The modifier function expects an argument of type reference to
      constant of the container type. The modifier function
      makes a deep copy of its argument. For instance:
   </p>


  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="member" type="string" minOccurs="unbounded"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef xml_schema::string member_type;
  typedef sequence&lt;member_type> member_sequence;
  typedef member_sequence::iterator member_iterator;
  typedef member_sequence::const_iterator member_const_iterator;

  // Accessors.
  //
  const member_sequence&amp;
  member () const;

  member_sequence&amp;
  member ();

  // Modifier.
  //
  void
  member (const member_sequence&amp;);

  ...

};
  </pre>

  <p>The <code>sequence</code> class template is defined in an
     implementation-specific namespace. It conforms to the
     sequence interface as defined by the ISO/ANSI Standard for
     C++ (ISO/IEC 14882:1998, Section 23.1.1, "Sequences").
     Practically, this means that you can treat such a sequence
     as if it was <code>std::vector</code>. Two notable extensions
     to the standard interface that are available only for
     sequences of non-fundamental C++ types are the addition of
     the overloaded <code>push_back</code> and <code>insert</code>
     as well as the <code>detach_back</code> and <code>detach</code>
     member functions. The additional <code>push_back</code> and
     <code>insert</code> functions accept an automatic pointer
     (<code>std::auto_ptr</code> or <code>std::unique_ptr</code>,
     depending on the C++ standard selected) to the
     element type instead of the constant reference. They assume
     ownership of the pointed to object and reset the passed
     automatic pointer. The <code>detach_back</code> and
     <code>detach</code> functions detach the element
     value from the sequence container and, by default, remove
     the element from the sequence. These additional functions
     have the following signatures:</p>

  <pre class="c++">
template &lt;typename X>
class sequence
{
public:
  ...

  void
  push_back (std::[auto|unique]_ptr&lt;X>)

  iterator
  insert (iterator position, std::[auto|unique]_ptr&lt;X>)

  std::[auto|unique]_ptr&lt;X>
  detach_back (bool pop = true);

  iterator
  detach (iterator position,
          std::[auto|unique]_ptr&lt;X>&amp; result,
          bool erase = true)

  ...
}
  </pre>

  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o)
{
  using xml_schema::string;

  object::member_sequence&amp; s (o.member ());

  // Iteration.
  //
  for (object::member_iterator i (s.begin ()); i != s.end (); ++i)
  {
    string&amp; value (*i);
  }

  // Modification.
  //
  s.push_back ("hello");  // deep copy

  // C++98 version.
  //
  std::auto_ptr&lt;string> p (new string ("hello"));
  s.push_back (p);        // assumes ownership
  p = s.detach_back ();   // detach and pop
  s.push_back (p);        // re-append

  // C++11 version.
  //
  std::unique_ptr&lt;string> p (new string ("hello"));
  s.push_back (std::move (p)); // assumes ownership
  p = s.detach_back ();        // detach and pop
  s.push_back (std::move (p)); // re-append

  // Setting a new container.
  //
  object::member_sequence n;
  n.push_back ("one");
  n.push_back ("two");
  o.member (n);           // deep copy
}
  </pre>

  <h3><a name="2.8.4">2.8.4 Element Order</a></h3>

  <p>C++/Tree is a "flattening" mapping in a sense that many levels of
     nested compositors (<code>choice</code> and <code>sequence</code>),
     all potentially with their own cardinalities, are in the end mapped
     to a flat set of elements with one of the three cardinality classes
     discussed in the previous sections. While this results in a simple
     and easy to use API for most types, in certain cases, the order of
     elements in the actual XML documents is not preserved once parsed
     into the object model. And sometimes such order has
     application-specific significance. As an example, consider a schema
     that defines a batch of bank transactions:</p>

  <pre class="xml">
&lt;complexType name="withdraw">
  &lt;sequence>
    &lt;element name="account" type="unsignedInt"/>
    &lt;element name="amount" type="unsignedInt"/>
  &lt;/sequence>
&lt;/complexType>

&lt;complexType name="deposit">
  &lt;sequence>
    &lt;element name="account" type="unsignedInt"/>
    &lt;element name="amount" type="unsignedInt"/>
  &lt;/sequence>
&lt;/complexType>

&lt;complexType name="batch">
  &lt;choice minOccurs="0" maxOccurs="unbounded">
    &lt;element name="withdraw" type="withdraw"/>
    &lt;element name="deposit" type="deposit"/>
  &lt;/choice>
&lt;/complexType>
  </pre>

  <p>The batch can contain any number of transactions in any order
     but the order of transactions in each actual batch is significant.
     For instance, consider what could happen if we reorder the
     transactions and apply all the withdrawals before deposits.</p>

  <p>For the <code>batch</code> schema type defined above the default
     C++/Tree mapping will produce a C++ class that contains a pair of
     sequence containers, one for each of the two elements. While this
     will capture the content (transactions), the order of this content
     as it appears in XML will be lost. Also, if we try to serialize the
     batch we just loaded back to XML, all the withdrawal transactions
     will appear before deposits.</p>

  <p>To overcome this limitation of a flattening mapping, C++/Tree
     allows us to mark certain XML Schema types, for which content
     order is important, as ordered.</p>

  <p>There are several command line options that control which
     schema types are treated as ordered. To make an individual
     type ordered, we use the <code>--ordered-type</code> option,
     for example:</p>

  <pre class="term">
--ordered-type batch
  </pre>

  <p>To automatically treat all the types that are derived from an ordered
     type also ordered, we use the <code>--ordered-type-derived</code>
     option. This is primarily useful if you would like to iterate
     over the complete hierarchy's content using the content order
     sequence (discussed below).</p>

  <p>Ordered types are also useful for handling mixed content. To
     automatically mark all the types with mixed content as ordered
     we use the <code>--ordered-type-mixed</code> option. For more
     information on handling mixed content see <a href="#2.13">Section
     2.13, "Mapping for Mixed Content Models"</a>.</p>

  <p>Finally, we can mark all the types in the schema we are
     compiling with the <code>--ordered-type-all</code> option.
     You should only resort to this option if all the types in
     your schema truly suffer from the loss of content
     order since, as we will discuss shortly, ordered types
     require extra effort to access and, especially, modify.
     See the
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a> for more information on
     these options.</p>

  <p>Once a type is marked ordered, C++/Tree alters its mapping
     in several ways. Firstly, for each local element, element
     wildcard (<a href="#2.12.4">Section 2.12.4, "Element Wildcard
     Order"</a>), and mixed content text (<a href="#2.13">Section
     2.13, "Mapping for Mixed Content Models"</a>) in this type, a
     content id constant is generated. Secondly, an addition sequence
     is added to the class that captures the content order. Here
     is how the mapping of our <code>batch</code> class changes
     once we make it ordered:</p>

  <pre class="c++">
class batch: public xml_schema::type
{
public:
  // withdraw
  //
  typedef withdraw withdraw_type;
  typedef sequence&lt;withdraw_type> withdraw_sequence;
  typedef withdraw_sequence::iterator withdraw_iterator;
  typedef withdraw_sequence::const_iterator withdraw_const_iterator;

  static const std::size_t withdraw_id = 1;

  const withdraw_sequence&amp;
  withdraw () const;

  withdraw_sequence&amp;
  withdraw ();

  void
  withdraw (const withdraw_sequence&amp;);

  // deposit
  //
  typedef deposit deposit_type;
  typedef sequence&lt;deposit_type> deposit_sequence;
  typedef deposit_sequence::iterator deposit_iterator;
  typedef deposit_sequence::const_iterator deposit_const_iterator;

  static const std::size_t deposit_id = 2;

  const deposit_sequence&amp;
  deposit () const;

  deposit_sequence&amp;
  deposit ();

  void
  deposit (const deposit_sequence&amp;);

  // content_order
  //
  typedef xml_schema::content_order content_order_type;
  typedef std::vector&lt;content_order_type> content_order_sequence;
  typedef content_order_sequence::iterator content_order_iterator;
  typedef content_order_sequence::const_iterator content_order_const_iterator;

  const content_order_sequence&amp;
  content_order () const;

  content_order_sequence&amp;
  content_order ();

  void
  content_order (const content_order_sequence&amp;);

  ...
};
  </pre>

  <p>Notice the <code>withdraw_id</code> and <code>deposit_id</code>
     content ids as well as the extra <code>content_order</code>
     sequence that does not correspond to any element in the
     schema definition. The other changes to the mapping for ordered
     types has to do with XML parsing and serialization code. During
     parsing the content order is captured in the <code>content_order</code>
     sequence while during serialization this sequence is used to
     determine the order in which content is serialized. The
     <code>content_order</code> sequence is also copied during
     copy construction and assigned during copy assignment. It is also
     taken into account during comparison.</p>

  <p>The entry type of the <code>content_order</code> sequence is the
     <code>xml_schema::content_order</code> type that has the following
     interface:</p>

  <pre class="c++">
namespace xml_schema
{
  struct content_order
  {
    content_order (std::size_t id, std::size_t index = 0);

    std::size_t id;
    std::size_t index;
  };

  bool
  operator== (const content_order&amp;, const content_order&amp;);

  bool
  operator!= (const content_order&amp;, const content_order&amp;);

  bool
  operator&lt; (const content_order&amp;, const content_order&amp;);
}
  </pre>

  <p>The <code>content_order</code> sequence describes the order of
     content (elements, including wildcards, as well as mixed content
     text). Each entry in this sequence consists of the content id
     (for example, <code>withdraw_id</code> or <code>deposit_id</code>
     in our case) as well as, for elements of the sequence cardinality
     class, an index into the corresponding sequence container (the
     index is unused for the one and optional cardinality classes).
     For example, in our case, if the content id is <code>withdraw_id</code>,
     then the index will point into the <code>withdraw</code> element
     sequence.</p>

  <p>With all this information we can now examine how to iterate over
     transaction in the batch in content order:</p>

  <pre class="c++">
batch&amp; b = ...

for (batch::content_order_const_iterator i (b.content_order ().begin ());
     i != b.content_order ().end ();
     ++i)
{
  switch (i->id)
  {
  case batch::withdraw_id:
    {
      const withdraw&amp; t (b.withdraw ()[i->index]);
      cerr &lt;&lt; t.account () &lt;&lt; " withdraw " &lt;&lt; t.amount () &lt;&lt; endl;
      break;
    }
  case batch::deposit_id:
    {
      const deposit&amp; t (b.deposit ()[i->index]);
      cerr &lt;&lt; t.account () &lt;&lt; " deposit " &lt;&lt; t.amount () &lt;&lt; endl;
      break;
    }
  default:
    {
      assert (false); // Unknown content id.
    }
  }
}
  </pre>

  <p>If we serialized our batch back to XML, we would also see that the
     order of transactions in the output is exactly the same as in the
     input rather than all the withdrawals first followed by all the
     deposits.</p>

  <p>The most complex aspect of working with ordered types is
     modifications. Now we not only need to change the content,
     but also remember to update the order information corresponding
     to this change. As a first example, we add a deposit transaction
     to the batch:</p>

  <pre class="c++">
using xml_schema::content_order;

batch::deposit_sequence&amp; d (b.deposit ());
batch::withdraw_sequence&amp; w (b.withdraw ());
batch::content_order_sequence&amp; co (b.content_order ());

d.push_back (deposit (123456789, 100000));
co.push_back (content_order (batch::deposit_id, d.size () - 1));
  </pre>

  <p>In the above example we first added the content (deposit
     transaction) and then updated the content order information
     by adding an entry with <code>deposit_id</code> content
     id and the index of the just added deposit transaction.</p>

  <p>Removing the last transaction can be easy if we know which
     transaction (deposit or withdrawal) is last:</p>

  <pre class="c++">
d.pop_back ();
co.pop_back ();
  </pre>

  <p>If, however, we do not know which transaction is last, then
     things get a bit more complicated:</p>

  <pre class="c++">
switch (co.back ().id)
{
case batch::withdraw_id:
  {
    d.pop_back ();
    break;
  }
case batch::deposit_id:
  {
    w.pop_back ();
    break;
  }
}

co.pop_back ();
  </pre>

  <p>The following example shows how to add a transaction at the
     beginning of the batch:</p>

  <pre class="c++">
w.push_back (withdraw (123456789, 100000));
co.insert (co.begin (),
           content_order (batch::withdraw_id, w.size () - 1));
  </pre>

  <p>Note also that when we merely modify the content of one
     of the elements in place, we do not need to update its
     order since it doesn't change. For example, here is how
     we can change the amount in the first withdrawal:</p>

  <pre class="c++">
w[0].amount (10000);
  </pre>

  <p>For the complete working code shown in this section refer to the
     <code>order/element</code> example in the
     <code>examples/cxx/tree/</code> directory in the XSD distribution.</p>

  <p>If both the base and derived types are ordered, then the
     content order sequence is only added to the base and the content
     ids are unique within the whole hierarchy. In this case
     the content order sequence for the derived type contains
     ordering information for both base and derived content.</p>

  <p>In some applications we may need to perform more complex
     content processing. For example, in our case, we may need
     to remove all the withdrawal transactions. The default
     container, <code>std::vector</code>, is not particularly
     suitable for such operations. What may be required by
     some applications is a multi-index container that not
     only allows us to iterate in content order similar to
     <code>std::vector</code> but also search by the content
     id as well as the content id and index pair.</p>

  <p>While C++/Tree does not provide this functionality by
     default, it allows us to specify a custom container
     type for content order with the <code>--order-container</code>
     command line option. The only requirement from the
     generated code side for such a container is to provide
     the <code>vector</code>-like <code>push_back()</code>,
     <code>size()</code>, and const iteration interfaces.</p>

  <p>As an example, here is how we can use the Boost Multi-Index
     container for content order. First we create the
     <code>content-order-container.hxx</code> header with the
     following definition (in C++11, use the alias template
     instead):</p>

  <pre class="c++">
#ifndef CONTENT_ORDER_CONTAINER
#define CONTENT_ORDER_CONTAINER

#include &lt;cstddef> // std::size_t

#include &lt;boost/multi_index_container.hpp>
#include &lt;boost/multi_index/member.hpp>
#include &lt;boost/multi_index/identity.hpp>
#include &lt;boost/multi_index/ordered_index.hpp>
#include &lt;boost/multi_index/random_access_index.hpp>

struct by_id {};
struct by_id_index {};

template &lt;typename T>
struct content_order_container:
  boost::multi_index::multi_index_container&lt;
    T,
    boost::multi_index::indexed_by&lt;
      boost::multi_index::random_access&lt;>,
      boost::multi_index::ordered_unique&lt;
        boost::multi_index::tag&lt;by_id_index>,
        boost::multi_index::identity&lt;T>
      >,
      boost::multi_index::ordered_non_unique&lt;
        boost::multi_index::tag&lt;by_id>,
        boost::multi_index::member&lt;T, std::size_t, &amp;T::id>
      >
    >
  >
{};

#endif
  </pre>

  <p>Next we add the following two XSD compiler options to include
     this header into every generated header file and to use the
     custom container type (see the XSD compiler command line manual
     for more information on shell quoting for the first option):</p>

  <pre class="term">
--hxx-prologue '#include "content-order-container.hxx"'
--order-container content_order_container
  </pre>

  <p>With these changes we can now use the multi-index functionality,
     for example, to search for a specific content id:</p>

  <pre class="c++">
typedef batch::content_order_sequence::index&lt;by_id>::type id_set;
typedef id_set::iterator id_iterator;

const id_set&amp; ids (b.content_order ().get&lt;by_id> ());

std::pair&lt;id_iterator, id_iterator> r (
  ids.equal_range (std::size_t (batch::deposit_id));

for (id_iterator i (r.first); i != r.second; ++i)
{
  const deposit&amp; t (b.deposit ()[i->index]);
  cerr &lt;&lt; t.account () &lt;&lt; " deposit " &lt;&lt; t.amount () &lt;&lt; endl;
}
  </pre>

  <h2><a name="2.9">2.9 Mapping for Global Elements</a></h2>

  <p>An XML Schema element definition is called global if it appears
     directly under the <code>schema</code> element.
     A global element is a valid root of an instance document. By
     default, a global element is mapped to a set of overloaded
     parsing and, optionally, serialization functions with the
     same name as the element. It is also possible to generate types
     for root elements instead of parsing and serialization functions.
     This is primarily useful to distinguish object models with the
     same root type but with different root elements. See
     <a href="#2.9.1">Section 2.9.1, "Element Types"</a> for details.
     It is also possible to request the generation of an element map
     which allows uniform parsing and serialization of multiple root
     elements. See <a href="#2.9.2">Section 2.9.2, "Element Map"</a>
     for details.
  </p>

  <p>The parsing functions read XML instance documents and return
     corresponding object models as an automatic pointer
     (<code>std::auto_ptr</code> or <code>std::unique_ptr</code>,
     depending on the C++ standard selected). Their signatures
     have the following pattern (<code>type</code> denotes
     element's type and <code>name</code> denotes element's
     name):
  </p>

  <pre class="c++">
std::[auto|unique]_ptr&lt;type>
name (....);
  </pre>

  <p>The process of parsing, including the exact signatures of the parsing
     functions, is the subject of <a href="#3">Chapter 3, "Parsing"</a>.
  </p>

  <p>The serialization functions write object models back to XML instance
     documents. Their signatures have the following pattern:
  </p>

  <pre class="c++">
void
name (&lt;stream type>&amp;, const type&amp;, ....);
  </pre>

  <p>The process of serialization, including the exact signatures of the
     serialization functions, is the subject of <a href="#4">Chapter 4,
     "Serialization"</a>.
  </p>


  <h3><a name="2.9.1">2.9.1 Element Types</a></h3>

  <p>The generation of element types is requested with the
     <code>--generate-element-type</code> option. With this option
     each global element is mapped to a C++ class with the
     same name as the element. Such a class is derived from
     <code>xml_schema::element_type</code> and contains the same set
     of type definitions, constructors, and member function as would a
     type containing a single element with the One cardinality class
     named <code>"value"</code>. In addition, the element type also
     contains a set of member functions for accessing the element
     name and namespace as well as its value in a uniform manner.
     For example:</p>

  <pre class="xml">
&lt;complexType name="type">
  &lt;sequence>
    ...
  &lt;/sequence>
&lt;/complexType>

&lt;element name="root" type="type"/>
  </pre>

<p>is mapped to:</p>

  <pre class="c++">
class type
{
  ...
};

class root: public xml_schema::element_type
{
public:
  // Element value.
  //
  typedef type value_type;

  const value_type&amp;
  value () const;

  value_type&amp;
  value ();

  void
  value (const value_type&amp;);

  void
  value (std::[auto|unique]_ptr&lt;value_type>);

  // Constructors.
  //
  root (const value_type&amp;);

  root (std::[auto|unique]_ptr&lt;value_type>);

  root (const xercesc::DOMElement&amp;, xml_schema::flags = 0);

  root (const root&amp;, xml_schema::flags = 0);

  virtual root*
  _clone (xml_schema::flags = 0) const;

  // Element name and namespace.
  //
  static const std::string&amp;
  name ();

  static const std::string&amp;
  namespace_ ();

  virtual const std::string&amp;
  _name () const;

  virtual const std::string&amp;
  _namespace () const;

  // Element value as xml_schema::type.
  //
  virtual const xml_schema::type*
  _value () const;

  virtual xml_schema::type*
  _value ();
};

void
operator&lt;&lt; (xercesc::DOMElement&amp;, const root&amp;);
  </pre>

  <p>The <code>xml_schema::element_type</code> class is a common
     base type for all element types and is defined as follows:</p>

  <pre class="c++">
namespace xml_schema
{
  class element_type
  {
  public:
    virtual
    ~element_type ();

    virtual element_type*
    _clone (flags f = 0) const = 0;

    virtual const std::basic_string&lt;C>&amp;
    _name () const = 0;

    virtual const std::basic_string&lt;C>&amp;
    _namespace () const = 0;

    virtual xml_schema::type*
    _value () = 0;

    virtual const xml_schema::type*
    _value () const = 0;
  };
}
  </pre>

  <p>The <code>_value()</code> member function returns a pointer to
     the element value or 0 if the element is of a fundamental C++
     type and therefore is not derived from <code>xml_schema::type</code>.
  </p>

  <p>Unlike parsing and serialization functions, element types
     are only capable of parsing and serializing from/to a
     <code>DOMElement</code> object. This means that the application
     will need to perform its own XML-to-DOM parsing and DOM-to-XML
     serialization. The following section describes a mechanism
     provided by the mapping to uniformly parse and serialize
     multiple root elements.</p>


  <h3><a name="2.9.2">2.9.2 Element Map</a></h3>

  <p>When element types are generated for root elements it is also
     possible to request the generation of an element map with the
     <code>--generate-element-map</code> option. The element map
     allows uniform parsing and serialization of multiple root
     elements via the common <code>xml_schema::element_type</code>
     base type. The <code>xml_schema::element_map</code> class is
     defined as follows:</p>

  <pre class="c++">
namespace xml_schema
{
  class element_map
  {
  public:
    static std::[auto|unique]_ptr&lt;xml_schema::element_type>
    parse (const xercesc::DOMElement&amp;, flags = 0);

    static void
    serialize (xercesc::DOMElement&amp;, const element_type&amp;);
  };
}
  </pre>

  <p>The <code>parse()</code> function creates the corresponding
     element type object based on the element name and namespace
     and returns it as an automatic pointer (<code>std::auto_ptr</code>
     or <code>std::unique_ptr</code>, depending on the C++ standard
     selected) to <code>xml_schema::element_type</code>.
     The <code>serialize()</code> function serializes the passed element
     object to <code>DOMElement</code>. Note that in case of
     <code>serialize()</code>, the <code>DOMElement</code> object
     should have the correct name and namespace. If no element type is
     available for an element, both functions throw the
     <code>xml_schema::no_element_info</code> exception:</p>

  <pre class="c++">
struct no_element_info: virtual exception
{
  no_element_info (const std::basic_string&lt;C>&amp; element_name,
                   const std::basic_string&lt;C>&amp; element_namespace);

  const std::basic_string&lt;C>&amp;
  element_name () const;

  const std::basic_string&lt;C>&amp;
  element_namespace () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The application can discover the actual type of the element
     object returned by <code>parse()</code> either using
     <code>dynamic_cast</code> or by comparing element names and
     namespaces. The following code fragments illustrate how the
     element map can be used:</p>

  <pre class="c++">
// Parsing.
//
DOMElement&amp; e = ... // Parse XML to DOM.

auto_ptr&lt;xml_schema::element_type> r (
  xml_schema::element_map::parse (e));

if (root1 r1 = dynamic_cast&lt;root1*> (r.get ()))
{
  ...
}
else if (r->_name == root2::name () &amp;&amp;
         r->_namespace () == root2::namespace_ ())
{
  root2&amp; r2 (static_cast&lt;root2&amp;> (*r));

  ...
}
  </pre>

  <pre class="c++">
// Serialization.
//
xml_schema::element_type&amp; r = ...

string name (r._name ());
string ns (r._namespace ());

DOMDocument&amp; doc = ... // Create a new DOMDocument with name and ns.
DOMElement&amp; e (*doc->getDocumentElement ());

xml_schema::element_map::serialize (e, r);

// Serialize DOMDocument to XML.
  </pre>

  <!-- -->

  <h2><a name="2.10">2.10 Mapping for Global Attributes</a></h2>

  <p>An XML Schema attribute definition is called global if it appears
     directly under the <code>schema</code> element. A global
     attribute does not have any mapping.
  </p>

  <!--
     When it is referenced from
     a local attribute definition (using the <code>ref</code> attribute)
     it is treated as a local attribute (see Section 2.8, "Mapping for
     Local Elements and Attributes").
  -->

  <h2><a name="2.11">2.11 Mapping for <code>xsi:type</code> and Substitution
      Groups</a></h2>

  <p>The mapping provides optional support for the XML Schema polymorphism
     features (<code>xsi:type</code> and substitution groups) which can
     be requested with the <code>--generate-polymorphic</code> option.
     When used, the dynamic type of a member may be different from
     its static type. Consider the following schema definition and
     instance document:
  </p>

  <pre class="xml">
&lt;!-- test.xsd -->
&lt;schema>
  &lt;complexType name="base">
    &lt;attribute name="text" type="string"/>
  &lt;/complexType>

  &lt;complexType name="derived">
    &lt;complexContent>
      &lt;extension base="base">
        &lt;attribute name="extra-text" type="string"/>
      &lt;/extension>
    &lt;/complexContent>
  &lt;/complexType>

  &lt;complexType name="root_type">
    &lt;sequence>
      &lt;element name="item" type="base" maxOccurs="unbounded"/>
    &lt;/sequence>
  &lt;/complexType>

  &lt;element name="root" type="root_type"/>
&lt;/schema>

&lt;!-- test.xml -->
&lt;root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  &lt;item text="hello"/>
  &lt;item text="hello" extra-text="world" xsi:type="derived"/>
&lt;/root>
  </pre>

  <p>In the resulting object model, the container for
     the <code>root::item</code> member will have two elements:
     the first element's type will be <code>base</code> while
     the second element's (dynamic) type will be
     <code>derived</code>. This can be discovered using the
     <code>dynamic_cast</code> operator as shown in the following
     example:
  </p>

  <pre class="c++">
void
f (root&amp; r)
{
  for (root::item_const_iterator i (r.item ().begin ());
       i != r.item ().end ()
       ++i)
  {
    if (derived* d = dynamic_cast&lt;derived*> (&amp;(*i)))
    {
      // derived
    }
    else
    {
      // base
    }
  }
}
  </pre>

  <p>The <code>_clone</code> virtual function should be used instead of
     copy constructors to make copies of members that might use
     polymorphism:
  </p>

  <pre class="c++">
void
f (root&amp; r)
{
  for (root::item_const_iterator i (r.item ().begin ());
       i != r.item ().end ()
       ++i)
  {
    std::auto_ptr&lt;base> c (i->_clone ());
  }
}
  </pre>

  <p>The mapping can often automatically determine which types are
     polymorphic based on the substitution group declarations. However,
     if your XML vocabulary is not using substitution groups or if
     substitution groups are defined in a separate schema, then you will
     need to use the <code>--polymorphic-type</code> option to specify
     which types are polymorphic. When using this option you only need
     to specify the root of a polymorphic type hierarchy and the mapping
     will assume that all the derived types are also polymorphic.
     Also note that you need to specify this option when compiling every
     schema file that references the polymorphic type. Consider the following
     two schemas as an example:</p>

  <pre class="xml">
&lt;!-- base.xsd -->
&lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  &lt;xs:complexType name="base">
    &lt;xs:sequence>
      &lt;xs:element name="b" type="xs:int"/>
    &lt;/xs:sequence>
  &lt;/xs:complexType>

  &lt;!-- substitution group root -->
  &lt;xs:element name="base" type="base"/>

&lt;/xs:schema>
  </pre>

  <pre class="xml">
&lt;!-- derived.xsd -->
&lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  &lt;include schemaLocation="base.xsd"/>

  &lt;xs:complexType name="derived">
    &lt;xs:complexContent>
      &lt;xs:extension base="base">
        &lt;xs:sequence>
          &lt;xs:element name="d" type="xs:string"/>
        &lt;/xs:sequence>
      &lt;/xs:extension>
    &lt;/xs:complexContent>
  &lt;/xs:complexType>

  &lt;xs:element name="derived" type="derived" substitutionGroup="base"/>

&lt;/xs:schema>
  </pre>

  <p>In this example we need to specify "<code>--polymorphic-type base</code>"
     when compiling both schemas because the substitution group is declared
     in a schema other than the one defining type <code>base</code>.</p>

  <p>You can also indicate that all types should be treated as polymorphic
     with the <code>--polymorphic-type-all</code>. However, this may result
     in slower generated code with a greater footprint.</p>


  <!-- Mapping for any and anyAttribute -->


  <h2><a name="2.12">2.12 Mapping for <code>any</code> and <code>anyAttribute</code></a></h2>

  <p>For the XML Schema <code>any</code> and <code>anyAttribute</code>
     wildcards an optional mapping can be requested with the
     <code>--generate-wildcard</code> option. The mapping represents
     the content matched by wildcards as DOM fragments. Because the
     DOM API is used to access such content, the Xerces-C++ runtime
     should be initialized by the application prior to parsing and
     should remain initialized for the lifetime of objects with
     the wildcard content. For more information on the Xerces-C++
     runtime initialization see <a href="#3.1">Section 3.1,
     "Initializing the Xerces-C++ Runtime"</a>.
  </p>

  <p>The mapping for <code>any</code> is similar to the mapping for
     local elements (see <a href="#2.8">Section 2.8, "Mapping for Local
     Elements and Attributes"</a>) except that the type used in the
     wildcard mapping is <code>xercesc::DOMElement</code>. As with local
     elements, the mapping divides all possible cardinality combinations
     into three cardinality classes: <i>one</i>, <i>optional</i>, and
     <i>sequence</i>.
  </p>

  <p>The mapping for <code>anyAttribute</code> represents the attributes
     matched by this wildcard as a set of <code>xercesc::DOMAttr</code>
     objects with a key being the attribute's name and namespace.</p>

  <p>Similar to local elements and attributes, the <code>any</code> and
     <code>anyAttribute</code> wildcards are mapped to a set of public type
     definitions (typedefs) and a set of public accessor and modifier
     functions. Type definitions have names derived from <code>"any"</code>
     for the <code>any</code> wildcard and <code>"any_attribute"</code>
     for the <code>anyAttribute</code> wildcard. The accessor and modifier
     functions are named <code>"any"</code> for the <code>any</code> wildcard
     and <code>"any_attribute"</code> for the <code>anyAttribute</code>
     wildcard. Subsequent wildcards in the same type have escaped names
     such as <code>"any1"</code> or <code>"any_attribute1"</code>.
  </p>

  <p>Because Xerces-C++ DOM nodes always belong to a <code>DOMDocument</code>,
     each type with a wildcard has an associated <code>DOMDocument</code>
     object. The reference to this object can be obtained using the accessor
     function called <code>dom_document</code>. The access to the document
     object from the application code may be necessary to create or modify
     the wildcard content. For example:
  </p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;any namespace="##other"/>
  &lt;/sequence>
  &lt;anyAttribute namespace="##other"/>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // any
  //
  const xercesc::DOMElement&amp;
  any () const;

  void
  any (const xercesc::DOMElement&amp;);

  ...

  // any_attribute
  //
  typedef attribute_set any_attribute_set;
  typedef any_attribute_set::iterator any_attribute_iterator;
  typedef any_attribute_set::const_iterator any_attribute_const_iterator;

  const any_attribute_set&amp;
  any_attribute () const;

  any_attribute_set&amp;
  any_attribute ();

  ...

  // DOMDocument object for wildcard content.
  //
  const xercesc::DOMDocument&amp;
  dom_document () const;

  xercesc::DOMDocument&amp;
  dom_document ();

  ...
};
  </pre>


  <p>Names and semantics of type definitions for the wildcards as well
     as signatures of the accessor and modifier functions depend on the
     wildcard type as well as the cardinality class for the <code>any</code>
     wildcard. They are described in the following sub-sections.
  </p>


  <h3><a name="2.12.1">2.12.1 Mapping for <code>any</code> with the One Cardinality Class</a></h3>

  <p>For <code>any</code> with the One cardinality class,
     there are no type definitions. The accessor functions come in
     constant and non-constant versions. The constant accessor function
     returns a constant reference to <code>xercesc::DOMElement</code> and
     can be used for read-only access. The non-constant version returns
     an unrestricted reference to <code>xercesc::DOMElement</code> and can
     be used for read-write access.
  </p>

  <p>The first modifier function expects an argument of type reference
     to constant <code>xercesc::DOMElement</code> and makes a deep copy
     of its argument. The second modifier function expects an argument of
     type pointer to <code>xercesc::DOMElement</code>. This modifier
     function assumes ownership of its argument and expects the element
     object to be created using the DOM document associated with this
     instance. For example:
  </p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;any namespace="##other"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Accessors.
  //
  const xercesc::DOMElement&amp;
  any () const;

  xercesc::DOMElement&amp;
  any ();

  // Modifiers.
  //
  void
  any (const xercesc::DOMElement&amp;);

  void
  any (xercesc::DOMElement*);

  ...

};
  </pre>


  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o, const xercesc::DOMElement&amp; e)
{
  using namespace xercesc;

  DOMElement&amp; e1 (o.any ());             // get
  o.any (e)                              // set, deep copy
  DOMDocument&amp; doc (o.dom_document ());
  o.any (doc.createElement (...));       // set, assumes ownership
}
  </pre>

  <h3><a name="2.12.2">2.12.2 Mapping for <code>any</code> with the Optional Cardinality Class</a></h3>

  <p>For <code>any</code> with the Optional cardinality class, the type
     definitions consist of an alias for the container type with name
     <code>any_optional</code> (or <code>any1_optional</code>, etc., for
     subsequent wildcards in the type definition).
  </p>

  <p>Unlike accessor functions for the One cardinality class, accessor
     functions for the Optional cardinality class return references to
     corresponding containers rather than directly to <code>DOMElement</code>.
     The accessor functions come in constant and non-constant versions.
     The constant accessor function returns a constant reference to
     the container and can be used for read-only access. The non-constant
     version returns an unrestricted reference to the container
     and can be used for read-write access.
  </p>

  <p>The modifier functions are overloaded for <code>xercesc::DOMElement</code>
     and the container type. The first modifier function expects an argument of
     type reference to constant <code>xercesc::DOMElement</code> and
     makes a deep copy of its argument. The second modifier function
     expects an argument of type pointer to <code>xercesc::DOMElement</code>.
     This modifier function assumes ownership of its argument and expects
     the element object to be created using the DOM document associated
     with this instance. The third modifier function expects an argument
     of type reference to constant of the container type and makes a
     deep copy of its argument. For instance:
  </p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;any namespace="##other" minOccurs="0"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef element_optional any_optional;

  // Accessors.
  //
  const any_optional&amp;
  any () const;

  any_optional&amp;
  any ();

  // Modifiers.
  //
  void
  any (const xercesc::DOMElement&amp;);

  void
  any (xercesc::DOMElement*);

  void
  any (const any_optional&amp;);

  ...

};
  </pre>


  <p>The <code>element_optional</code> container is a
     specialization of the <code>optional</code> class template described
     in <a href="#2.8.2">Section 2.8.2, "Mapping for Members with the Optional
     Cardinality Class"</a>. Its interface is presented below:
  </p>

  <pre class="c++">
class element_optional
{
public:
  explicit
  element_optional (xercesc::DOMDocument&amp;);

  // Makes a deep copy.
  //
  element_optional (const xercesc::DOMElement&amp;, xercesc::DOMDocument&amp;);

  // Assumes ownership.
  //
  element_optional (xercesc::DOMElement*, xercesc::DOMDocument&amp;);

  element_optional (const element_optional&amp;, xercesc::DOMDocument&amp;);

public:
  element_optional&amp;
  operator= (const xercesc::DOMElement&amp;);

  element_optional&amp;
  operator= (const element_optional&amp;);

  // Pointer-like interface.
  //
public:
  const xercesc::DOMElement*
  operator-> () const;

  xercesc::DOMElement*
  operator-> ();

  const xercesc::DOMElement&amp;
  operator* () const;

  xercesc::DOMElement&amp;
  operator* ();

  typedef void (element_optional::*bool_convertible) ();
  operator bool_convertible () const;

  // Get/set interface.
  //
public:
  bool
  present () const;

  const xercesc::DOMElement&amp;
  get () const;

  xercesc::DOMElement&amp;
  get ();

  // Makes a deep copy.
  //
  void
  set (const xercesc::DOMElement&amp;);

  // Assumes ownership.
  //
  void
  set (xercesc::DOMElement*);

  void
  reset ();
};

bool
operator== (const element_optional&amp;, const element_optional&amp;);

bool
operator!= (const element_optional&amp;, const element_optional&amp;);
  </pre>


  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o, const xercesc::DOMElement&amp; e)
{
  using namespace xercesc;

  DOMDocument&amp; doc (o.dom_document ());

  if (o.any ().present ())                  // test
  {
    DOMElement&amp; e1 (o.any ().get ());       // get
    o.any ().set (e);                       // set, deep copy
    o.any ().set (doc.createElement (...)); // set, assumes ownership
    o.any ().reset ();                      // reset
  }

  // Same as above but using pointer notation:
  //
  if (o.member ())                          // test
  {
    DOMElement&amp; e1 (*o.any ());             // get
    o.any (e);                              // set, deep copy
    o.any (doc.createElement (...));        // set, assumes ownership
    o.any ().reset ();                      // reset
  }
}
  </pre>



  <h3><a name="2.12.3">2.12.3 Mapping for <code>any</code> with the Sequence Cardinality Class</a></h3>

  <p>For <code>any</code> with the Sequence cardinality class, the type
     definitions consist of an alias of the container type with name
     <code>any_sequence</code> (or <code>any1_sequence</code>, etc., for
     subsequent wildcards in the type definition), an alias of the iterator
     type with name <code>any_iterator</code> (or <code>any1_iterator</code>,
     etc., for subsequent wildcards in the type definition), and an alias
     of the constant iterator type with name <code>any_const_iterator</code>
     (or <code>any1_const_iterator</code>, etc., for subsequent wildcards
     in the type definition).
  </p>

  <p>The accessor functions come in constant and non-constant versions.
     The constant accessor function returns a constant reference to the
     container and can be used for read-only access. The non-constant
     version returns an unrestricted reference to the container and can
     be used for read-write access.
  </p>

  <p>The modifier function expects an argument of type reference to
     constant of the container type. The modifier function makes
     a deep copy of its argument. For instance:
  </p>


  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;any namespace="##other" minOccurs="unbounded"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef element_sequence any_sequence;
  typedef any_sequence::iterator any_iterator;
  typedef any_sequence::const_iterator any_const_iterator;

  // Accessors.
  //
  const any_sequence&amp;
  any () const;

  any_sequence&amp;
  any ();

  // Modifier.
  //
  void
  any (const any_sequence&amp;);

  ...

};
  </pre>

  <p>The <code>element_sequence</code> container is a
     specialization of the <code>sequence</code> class template described
     in <a href="#2.8.3">Section 2.8.3, "Mapping for Members with the
     Sequence Cardinality Class"</a>. Its interface is similar to
     the sequence interface as defined by the ISO/ANSI Standard for
     C++ (ISO/IEC 14882:1998, Section 23.1.1, "Sequences") and is
     presented below:
  </p>

  <pre class="c++">
class element_sequence
{
public:
  typedef xercesc::DOMElement        value_type;
  typedef xercesc::DOMElement*       pointer;
  typedef const xercesc::DOMElement* const_pointer;
  typedef xercesc::DOMElement&amp;       reference;
  typedef const xercesc::DOMElement&amp; const_reference;

  typedef &lt;implementation-defined>   iterator;
  typedef &lt;implementation-defined>   const_iterator;
  typedef &lt;implementation-defined>   reverse_iterator;
  typedef &lt;implementation-defined>   const_reverse_iterator;

  typedef &lt;implementation-defined>   size_type;
  typedef &lt;implementation-defined>   difference_type;
  typedef &lt;implementation-defined>   allocator_type;

public:
  explicit
  element_sequence (xercesc::DOMDocument&amp;);

  // DOMElement cannot be default-constructed.
  //
  // explicit
  // element_sequence (size_type n);

  element_sequence (size_type n,
                    const xercesc::DOMElement&amp;,
                    xercesc::DOMDocument&amp;);

  template &lt;typename I>
  element_sequence (const I&amp; begin,
                    const I&amp; end,
                    xercesc::DOMDocument&amp;);

  element_sequence (const element_sequence&amp;, xercesc::DOMDocument&amp;);

  element_sequence&amp;
  operator= (const element_sequence&amp;);

public:
  void
  assign (size_type n, const xercesc::DOMElement&amp;);

  template &lt;typename I>
  void
  assign (const I&amp; begin, const I&amp; end);

public:
  // This version of resize can only be used to shrink the
  // sequence because DOMElement cannot be default-constructed.
  //
  void
  resize (size_type);

  void
  resize (size_type, const xercesc::DOMElement&amp;);

public:
  size_type
  size () const;

  size_type
  max_size () const;

  size_type
  capacity () const;

  bool
  empty () const;

  void
  reserve (size_type);

  void
  clear ();

public:
  const_iterator
  begin () const;

  const_iterator
  end () const;

  iterator
  begin ();

  iterator
  end ();

  const_reverse_iterator
  rbegin () const;

  const_reverse_iterator
  rend () const

    reverse_iterator
  rbegin ();

  reverse_iterator
  rend ();

public:
  xercesc::DOMElement&amp;
  operator[] (size_type);

  const xercesc::DOMElement&amp;
  operator[] (size_type) const;

  xercesc::DOMElement&amp;
  at (size_type);

  const xercesc::DOMElement&amp;
  at (size_type) const;

  xercesc::DOMElement&amp;
  front ();

  const xercesc::DOMElement&amp;
  front () const;

  xercesc::DOMElement&amp;
  back ();

  const xercesc::DOMElement&amp;
  back () const;

public:
  // Makes a deep copy.
  //
  void
  push_back (const xercesc::DOMElement&amp;);

  // Assumes ownership.
  //
  void
  push_back (xercesc::DOMElement*);

  void
  pop_back ();

  // Makes a deep copy.
  //
  iterator
  insert (iterator position, const xercesc::DOMElement&amp;);

  // Assumes ownership.
  //
  iterator
  insert (iterator position, xercesc::DOMElement*);

  void
  insert (iterator position, size_type n, const xercesc::DOMElement&amp;);

  template &lt;typename I>
  void
  insert (iterator position, const I&amp; begin, const I&amp; end);

  iterator
  erase (iterator position);

  iterator
  erase (iterator begin, iterator end);

public:
  // Note that the DOMDocument object of the two sequences being
  // swapped should be the same.
  //
  void
  swap (sequence&amp; x);
};

inline bool
operator== (const element_sequence&amp;, const element_sequence&amp;);

inline bool
operator!= (const element_sequence&amp;, const element_sequence&amp;);
  </pre>


  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o, const xercesc::DOMElement&amp; e)
{
  using namespace xercesc;

  object::any_sequence&amp; s (o.any ());

  // Iteration.
  //
  for (object::any_iterator i (s.begin ()); i != s.end (); ++i)
  {
    DOMElement&amp; e (*i);
  }

  // Modification.
  //
  s.push_back (e);                       // deep copy
  DOMDocument&amp; doc (o.dom_document ());
  s.push_back (doc.createElement (...)); // assumes ownership
}
  </pre>

  <h3><a name="2.12.4">2.12.4 Element Wildcard Order</a></h3>

  <p>Similar to elements, element wildcards in ordered types
     (<a href="#2.8.4">Section 2.8.4, "Element Order"</a>) are assigned
     content ids and are included in the content order sequence.
     Continuing with the bank transactions example started in Section
     2.8.4, we can extend the batch by allowing custom transactions:</p>

  <pre class="xml">
&lt;complexType name="batch">
  &lt;choice minOccurs="0" maxOccurs="unbounded">
    &lt;element name="withdraw" type="withdraw"/>
    &lt;element name="deposit" type="deposit"/>
    &lt;any namespace="##other" processContents="lax"/>
  &lt;/choice>
&lt;/complexType>
  </pre>

  <p>This will lead to the following changes in the generated
     <code>batch</code> C++ class:</p>

  <pre class="c++">
class batch: public xml_schema::type
{
public:
  ...

  // any
  //
  typedef element_sequence any_sequence;
  typedef any_sequence::iterator any_iterator;
  typedef any_sequence::const_iterator any_const_iterator;

  static const std::size_t any_id = 3UL;

  const any_sequence&amp;
  any () const;

  any_sequence&amp;
  any ();

  void
  any (const any_sequence&amp;);

  ...
};
  </pre>

  <p>With this change we also need to update the iteration code to handle
     the new content id:</p>

  <pre class="c++">
for (batch::content_order_const_iterator i (b.content_order ().begin ());
     i != b.content_order ().end ();
     ++i)
{
  switch (i->id)
  {
    ...

  case batch::any_id:
    {
      const DOMElement&amp; e (b.any ()[i->index]);
      ...
      break;
    }

    ...
  }
}
  </pre>

  <p>For the complete working code that shows the use of wildcards in
     ordered types refer to the <code>order/element</code> example in
     the <code>examples/cxx/tree/</code> directory in the XSD
     distribution.</p>

  <h3><a name="2.12.5">2.12.5 Mapping for <code>anyAttribute</code></a></h3>

  <p>For <code>anyAttribute</code> the type definitions consist of an alias
     of the container type with name <code>any_attribute_set</code>
     (or <code>any1_attribute_set</code>, etc., for subsequent wildcards
     in the type definition), an alias of the iterator type with name
     <code>any_attribute_iterator</code> (or <code>any1_attribute_iterator</code>,
     etc., for subsequent wildcards in the type definition), and an alias
     of the constant iterator type with name <code>any_attribute_const_iterator</code>
     (or <code>any1_attribute_const_iterator</code>, etc., for subsequent
     wildcards in the type definition).
  </p>

  <p>The accessor functions come in constant and non-constant versions.
     The constant accessor function returns a constant reference to the
     container and can be used for read-only access. The non-constant
     version returns an unrestricted reference to the container and can
     be used for read-write access.
  </p>

  <p>The modifier function expects an argument of type reference to
     constant of the container type. The modifier function makes
     a deep copy of its argument. For instance:
  </p>


  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    ...
  &lt;/sequence>
  &lt;anyAttribute namespace="##other"/>
&lt;/complexType>
  </pre>

  <p>is mapped to:</p>

  <pre class="c++">
class object: public xml_schema::type
{
public:
  // Type definitions.
  //
  typedef attribute_set any_attribute_set;
  typedef any_attribute_set::iterator any_attribute_iterator;
  typedef any_attribute_set::const_iterator any_attribute_const_iterator;

  // Accessors.
  //
  const any_attribute_set&amp;
  any_attribute () const;

  any_attribute_set&amp;
  any_attribute ();

  // Modifier.
  //
  void
  any_attribute (const any_attribute_set&amp;);

  ...

};
  </pre>

  <p>The <code>attribute_set</code> class is an associative container
     similar to the <code>std::set</code> class template as defined by
     the ISO/ANSI Standard for C++ (ISO/IEC 14882:1998, Section 23.3.3,
     "Class template set") with the key being the attribute's name
     and namespace. Unlike <code>std::set</code>, <code>attribute_set</code>
     allows searching using names and namespaces instead of
     <code>xercesc::DOMAttr</code> objects. It is defined in an
     implementation-specific namespace and its interface is presented
     below:
  </p>

  <pre class="c++">
class attribute_set
{
public:
  typedef xercesc::DOMAttr         key_type;
  typedef xercesc::DOMAttr         value_type;
  typedef xercesc::DOMAttr*        pointer;
  typedef const xercesc::DOMAttr*  const_pointer;
  typedef xercesc::DOMAttr&amp;        reference;
  typedef const xercesc::DOMAttr&amp;  const_reference;

  typedef &lt;implementation-defined> iterator;
  typedef &lt;implementation-defined> const_iterator;
  typedef &lt;implementation-defined> reverse_iterator;
  typedef &lt;implementation-defined> const_reverse_iterator;

  typedef &lt;implementation-defined> size_type;
  typedef &lt;implementation-defined> difference_type;
  typedef &lt;implementation-defined> allocator_type;

public:
  attribute_set (xercesc::DOMDocument&amp;);

  template &lt;typename I>
  attribute_set (const I&amp; begin, const I&amp; end, xercesc::DOMDocument&amp;);

  attribute_set (const attribute_set&amp;, xercesc::DOMDocument&amp;);

  attribute_set&amp;
  operator= (const attribute_set&amp;);

public:
  const_iterator
  begin () const;

  const_iterator
  end () const;

  iterator
  begin ();

  iterator
  end ();

  const_reverse_iterator
  rbegin () const;

  const_reverse_iterator
  rend () const;

  reverse_iterator
  rbegin ();

  reverse_iterator
  rend ();

public:
  size_type
  size () const;

  size_type
  max_size () const;

  bool
  empty () const;

  void
  clear ();

public:
  // Makes a deep copy.
  //
  std::pair&lt;iterator, bool>
  insert (const xercesc::DOMAttr&amp;);

  // Assumes ownership.
  //
  std::pair&lt;iterator, bool>
  insert (xercesc::DOMAttr*);

  // Makes a deep copy.
  //
  iterator
  insert (iterator position, const xercesc::DOMAttr&amp;);

  // Assumes ownership.
  //
  iterator
  insert (iterator position, xercesc::DOMAttr*);

  template &lt;typename I>
  void
  insert (const I&amp; begin, const I&amp; end);

public:
  void
  erase (iterator position);

  size_type
  erase (const std::basic_string&lt;C>&amp; name);

  size_type
  erase (const std::basic_string&lt;C>&amp; namespace_,
         const std::basic_string&lt;C>&amp; name);

  size_type
  erase (const XMLCh* name);

  size_type
  erase (const XMLCh* namespace_, const XMLCh* name);

  void
  erase (iterator begin, iterator end);

public:
  size_type
  count (const std::basic_string&lt;C>&amp; name) const;

  size_type
  count (const std::basic_string&lt;C>&amp; namespace_,
         const std::basic_string&lt;C>&amp; name) const;

  size_type
  count (const XMLCh* name) const;

  size_type
  count (const XMLCh* namespace_, const XMLCh* name) const;

  iterator
  find (const std::basic_string&lt;C>&amp; name);

  iterator
  find (const std::basic_string&lt;C>&amp; namespace_,
        const std::basic_string&lt;C>&amp; name);

  iterator
  find (const XMLCh* name);

  iterator
  find (const XMLCh* namespace_, const XMLCh* name);

  const_iterator
  find (const std::basic_string&lt;C>&amp; name) const;

  const_iterator
  find (const std::basic_string&lt;C>&amp; namespace_,
        const std::basic_string&lt;C>&amp; name) const;

  const_iterator
  find (const XMLCh* name) const;

  const_iterator
  find (const XMLCh* namespace_, const XMLCh* name) const;

public:
  // Note that the DOMDocument object of the two sets being
  // swapped should be the same.
  //
  void
  swap (attribute_set&amp;);
};

bool
operator== (const attribute_set&amp;, const attribute_set&amp;);

bool
operator!= (const attribute_set&amp;, const attribute_set&amp;);
  </pre>

  <p>The following code shows how one could use this mapping:</p>

  <pre class="c++">
void
f (object&amp; o, const xercesc::DOMAttr&amp; a)
{
  using namespace xercesc;

  object::any_attribute_set&amp; s (o.any_attribute ());

  // Iteration.
  //
  for (object::any_attribute_iterator i (s.begin ()); i != s.end (); ++i)
  {
    DOMAttr&amp; a (*i);
  }

  // Modification.
  //
  s.insert (a);                         // deep copy
  DOMDocument&amp; doc (o.dom_document ());
  s.insert (doc.createAttribute (...)); // assumes ownership

  // Searching.
  //
  object::any_attribute_iterator i (s.find ("name"));
  i = s.find ("http://www.w3.org/XML/1998/namespace", "lang");
}
  </pre>

  <!-- Mapping for Mixed Content Models -->

  <h2><a name="2.13">2.13 Mapping for Mixed Content Models</a></h2>

  <p>For XML Schema types with mixed content models C++/Tree provides
     mapping support only if the type is marked as ordered
     (<a href="#2.8.4">Section 2.8.4, "Element Order"</a>). Use the
     <code>--ordered-type-mixed</code> XSD compiler option to
     automatically mark all types with mixed content as ordered.</p>

  <p>For an ordered type with mixed content, C++/Tree adds an extra
     text content sequence that is used to store the text fragments.
     This text content sequence is also assigned the content id and
     its entries are included in the content order sequence, just
     like elements. As a result, it is possible to capture the order
     between elements and text fragments.</p>

  <p>As an example, consider the following schema that describes text
     with embedded links:</p>

  <pre class="xml">
&lt;complexType name="anchor">
  &lt;simpleContent>
    &lt;extension base="string">
      &lt;attribute name="href" type="anyURI" use="required"/>
    &lt;/extension>
  &lt;/simpleContent>
&lt;/complexType>

&lt;complexType name="text" mixed="true">
  &lt;sequence>
    &lt;element name="a" type="anchor" minOccurs="0" maxOccurs="unbounded"/>
  &lt;/sequence>
&lt;/complexType>
  </pre>

  <p>The generated <code>text</code> C++ class will provide the following
     API (assuming it is marked as ordered):</p>

  <pre class="c++">
class text: public xml_schema::type
{
public:
  // a
  //
  typedef anchor a_type;
  typedef sequence&lt;a_type> a_sequence;
  typedef a_sequence::iterator a_iterator;
  typedef a_sequence::const_iterator a_const_iterator;

  static const std::size_t a_id = 1UL;

  const a_sequence&amp;
  a () const;

  a_sequence&amp;
  a ();

  void
  a (const a_sequence&amp;);

  // text_content
  //
  typedef xml_schema::string text_content_type;
  typedef sequence&lt;text_content_type> text_content_sequence;
  typedef text_content_sequence::iterator text_content_iterator;
  typedef text_content_sequence::const_iterator text_content_const_iterator;

  static const std::size_t text_content_id = 2UL;

  const text_content_sequence&amp;
  text_content () const;

  text_content_sequence&amp;
  text_content ();

  void
  text_content (const text_content_sequence&amp;);

  // content_order
  //
  typedef xml_schema::content_order content_order_type;
  typedef std::vector&lt;content_order_type> content_order_sequence;
  typedef content_order_sequence::iterator content_order_iterator;
  typedef content_order_sequence::const_iterator content_order_const_iterator;

  const content_order_sequence&amp;
  content_order () const;

  content_order_sequence&amp;
  content_order ();

  void
  content_order (const content_order_sequence&amp;);

  ...
};
  </pre>

  <p>Given this interface we can iterate over both link elements
     and text in content order. The following code fragment converts
     our format to plain text with references.</p>

  <pre class="c++">
const text&amp; t = ...

for (text::content_order_const_iterator i (t.content_order ().begin ());
     i != t.content_order ().end ();
     ++i)
{
  switch (i->id)
  {
  case text::a_id:
    {
      const anchor&amp; a (t.a ()[i->index]);
      cerr &lt;&lt; a &lt;&lt; "[" &lt;&lt; a.href () &lt;&lt; "]";
      break;
    }
  case text::text_content_id:
    {
      const xml_schema::string&amp; s (t.text_content ()[i->index]);
      cerr &lt;&lt; s;
      break;
    }
  default:
    {
      assert (false); // Unknown content id.
    }
  }
}
  </pre>

  <p>For the complete working code that shows the use of mixed content
     in ordered types refer to the <code>order/mixed</code> example in
     the <code>examples/cxx/tree/</code> directory in the XSD
     distribution.</p>

  <!-- Parsing -->


  <h1><a name="3">3 Parsing</a></h1>

  <p>This chapter covers various aspects of parsing XML instance
     documents in order to obtain corresponding tree-like object
     model.
  </p>

  <p>Each global XML Schema element in the form:</p>

  <pre class="xml">
&lt;element name="name" type="type"/>
  </pre>

  <p>is mapped to 14 overloaded C++ functions in the form:</p>

  <pre class="c++">
// Read from a URI or a local file.
//

std::[auto|unique]_ptr&lt;type>
name (const std::basic_string&lt;C>&amp; uri,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (const std::basic_string&lt;C>&amp; uri,
      xml_schema::error_handler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (const std::basic_string&lt;C>&amp; uri,
      xercesc::DOMErrorHandler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());


// Read from std::istream.
//

std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      xml_schema::error_handler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      xercesc::DOMErrorHandler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());


std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      const std::basic_string&lt;C>&amp; id,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      const std::basic_string&lt;C>&amp; id,
      xml_schema::error_handler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (std::istream&amp;,
      const std::basic_string&lt;C>&amp; id,
      xercesc::DOMErrorHandler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());


// Read from InputSource.
//

std::[auto|unique]_ptr&lt;type>
name (xercesc::InputSource&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (xercesc::InputSource&amp;,
      xml_schema::error_handler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (xercesc::InputSource&amp;,
      xercesc::DOMErrorHandler&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());


// Read from DOM.
//

std::[auto|unique]_ptr&lt;type>
name (const xercesc::DOMDocument&amp;,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());

std::[auto|unique]_ptr&lt;type>
name (xml_schema::dom::[auto|unique]_ptr&lt;xercesc::DOMDocument>,
      xml_schema::flags = 0,
      const xml_schema::properties&amp; = xml_schema::properties ());
  </pre>

  <p>You can choose between reading an XML instance from a local file,
     URI, <code>std::istream</code>, <code>xercesc::InputSource</code>,
     or a pre-parsed DOM instance in the form of
     <code>xercesc::DOMDocument</code>. All the parsing functions
     return a dynamically allocated object model as either
     <code>std::auto_ptr</code> or <code>std::unique_ptr</code>,
     depending on the C++ standard selected. Each of these parsing
     functions is discussed in more detail in the following sections.
  </p>

  <h2><a name="3.1">3.1 Initializing the Xerces-C++ Runtime</a></h2>

  <p>Some parsing functions expect you to initialize the Xerces-C++
     runtime while others initialize and terminate it as part of their
     work. The general rule is as follows: if a function has any arguments
     or return a value that is an instance of a Xerces-C++ type, then
     this function expects you to initialize the Xerces-C++ runtime.
     Otherwise, the function initializes and terminates the runtime for
     you. Note that it is legal to have nested calls to the Xerces-C++
     initialize and terminate functions as long as the calls are balanced.
  </p>

  <p>You can instruct parsing functions that initialize and terminate
     the runtime not to do so by passing the
     <code>xml_schema::flags::dont_initialize</code> flag (see
     <a href="#3.2">Section 3.2, "Flags and Properties"</a>).
  </p>


  <h2><a name="3.2">3.2 Flags and Properties</a></h2>

  <p>Parsing flags and properties are the last two arguments of every
     parsing function. They allow you to fine-tune the process of
     instance validation and parsing. Both arguments are optional.
  </p>


  <p>The following flags are recognized by the parsing functions:</p>

  <dl>
    <dt><code>xml_schema::flags::keep_dom</code></dt>
    <dd>Keep association between DOM nodes and the resulting
        object model nodes. For more information about DOM association
        refer to <a href="#5.1">Section 5.1, "DOM Association"</a>.</dd>

    <dt><code>xml_schema::flags::own_dom</code></dt>
    <dd>Assume ownership of the DOM document passed. This flag only
        makes sense together with the <code>keep_dom</code> flag in
        the call to the parsing function with the
        <code>xml_schema::dom::[auto|unique]_ptr&lt;DOMDocument></code>
        argument.</dd>

    <dt><code>xml_schema::flags::dont_validate</code></dt>
    <dd>Do not validate instance documents against schemas.</dd>

    <dt><code>xml_schema::flags::dont_initialize</code></dt>
    <dd>Do not initialize the Xerces-C++ runtime.</dd>
  </dl>

  <p>You can pass several flags by combining them using the bit-wise OR
     operator. For example:</p>

  <pre class="c++">
using xml_schema::flags;

std::auto_ptr&lt;type> r (
  name ("test.xml", flags::keep_dom | flags::dont_validate));
  </pre>

  <p>By default, validation of instance documents is turned on even
     though parsers generated by XSD do not assume instance
     documents are valid. They include a number of checks that prevent
     construction of inconsistent object models. This,
     however, does not mean that an instance document that was
     successfully parsed by the XSD-generated parsers is
     valid per the corresponding schema. If an instance document is not
     "valid enough" for the generated parsers to construct consistent
     object model, one of the exceptions defined in
     <code>xml_schema</code> namespace is thrown (see
     <a href="#3.3">Section 3.3, "Error Handling"</a>).
  </p>

  <p>For more information on the Xerces-C++ runtime initialization
     refer to <a href="#3.1">Section 3.1, "Initializing the Xerces-C++
     Runtime"</a>.
  </p>

  <p>The <code>xml_schema::properties</code> class allows you to
     programmatically specify schema locations to be used instead
     of those specified with the <code>xsi::schemaLocation</code>
     and <code>xsi::noNamespaceSchemaLocation</code> attributes
     in instance documents. The interface of the <code>properties</code>
     class is presented below:
  </p>

  <pre class="c++">
class properties
{
public:
  void
  schema_location (const std::basic_string&lt;C>&amp; namespace_,
                   const std::basic_string&lt;C>&amp; location);
  void
  no_namespace_schema_location (const std::basic_string&lt;C>&amp; location);
};
  </pre>

  <p>Note that all locations are relative to an instance document unless
     they are URIs. For example, if you want to use a local file as your
     schema, then you will need to pass
     <code>file:///absolute/path/to/your/schema</code> as the location
     argument.
  </p>

  <h2><a name="3.3">3.3 Error Handling</a></h2>

  <p>As discussed in <a href="#2.2">Section 2.2, "Error Handling"</a>,
     the mapping uses the C++ exception handling mechanism as its primary
     way of reporting error conditions. However, to handle recoverable
     parsing and validation errors and warnings, a callback interface maybe
     preferred by the application.</p>

  <p>To better understand error handling and reporting strategies employed
     by the parsing functions, it is useful to know that the
     transformation of an XML instance document to a statically-typed
     tree happens in two stages. The first stage, performed by Xerces-C++,
     consists of parsing an XML document into a DOM instance. For short,
     we will call this stage the XML-DOM stage. Validation, if not disabled,
     happens during this stage. The second stage,
     performed by the generated parsers, consist of parsing the DOM
     instance into the statically-typed tree. We will call this stage
     the DOM-Tree stage. Additional checks are performed during this
     stage in order to prevent construction of inconsistent tree which
     could otherwise happen when validation is disabled, for example.</p>

  <p>All parsing functions except the one that operates on a DOM instance
     come in overloaded triples. The first function in such a triple
     reports error conditions exclusively by throwing exceptions. It
     accumulates all the parsing and validation errors of the XML-DOM
     stage and throws them in a single instance of the
     <code>xml_schema::parsing</code> exception (described below).
     The second and the third functions in the triple use callback
     interfaces to report parsing and validation errors and warnings.
     The two callback interfaces are <code>xml_schema::error_handler</code>
     and <code>xercesc::DOMErrorHandler</code>. For more information
     on the <code>xercesc::DOMErrorHandler</code> interface refer to
     the Xerces-C++ documentation. The <code>xml_schema::error_handler</code>
     interface is presented below:
  </p>

  <pre class="c++">
class error_handler
{
public:
  struct severity
  {
    enum value
    {
      warning,
      error,
      fatal
    };
  };

  virtual bool
  handle (const std::basic_string&lt;C>&amp; id,
          unsigned long line,
          unsigned long column,
          severity,
          const std::basic_string&lt;C>&amp; message) = 0;

  virtual
  ~error_handler ();
};
  </pre>

  <p>The <code>id</code> argument of the <code>error_handler::handle</code>
     function identifies the resource being parsed (e.g., a file name or
     URI).
  </p>

  <p>By returning <code>true</code> from the <code>handle</code> function
     you instruct the parser to recover and continue parsing. Returning
     <code>false</code> results in termination of the parsing process.
     An error with the <code>fatal</code> severity level results in
     termination of the parsing process no matter what is returned from
     the <code>handle</code> function. It is safe to throw an exception
     from the <code>handle</code> function.
  </p>

  <p>The DOM-Tree stage reports error conditions exclusively by throwing
     exceptions. Individual exceptions thrown by the parsing functions
     are described in the following sub-sections.
  </p>


  <h3><a name="3.3.1">3.3.1 <code>xml_schema::parsing</code></a></h3>

  <pre class="c++">
struct severity
{
  enum value
  {
    warning,
    error
  };

  severity (value);
  operator value () const;
};

struct error
{
  error (severity,
         const std::basic_string&lt;C>&amp; id,
         unsigned long line,
         unsigned long column,
         const std::basic_string&lt;C>&amp; message);

  severity
  severity () const;

  const std::basic_string&lt;C>&amp;
  id () const;

  unsigned long
  line () const;

  unsigned long
  column () const;

  const std::basic_string&lt;C>&amp;
  message () const;
};

std::basic_ostream&lt;C>&amp;
operator&lt;&lt; (std::basic_ostream&lt;C>&amp;, const error&amp;);

struct diagnostics: std::vector&lt;error>
{
};

std::basic_ostream&lt;C>&amp;
operator&lt;&lt; (std::basic_ostream&lt;C>&amp;, const diagnostics&amp;);

struct parsing: virtual exception
{
  parsing ();
  parsing (const diagnostics&amp;);

  const diagnostics&amp;
  diagnostics () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::parsing</code> exception is thrown if there
     were parsing or validation errors reported during the XML-DOM stage.
     If no callback interface was provided to the parsing function, the
     exception contains a list of errors and warnings accessible using
     the <code>diagnostics</code> function. The usual conditions when
     this exception is thrown include malformed XML instances and, if
     validation is turned on, invalid instance documents.
  </p>

  <h3><a name="3.3.2">3.3.2 <code>xml_schema::expected_element</code></a></h3>

  <pre class="c++">
struct expected_element: virtual exception
{
  expected_element (const std::basic_string&lt;C>&amp; name,
                    const std::basic_string&lt;C>&amp; namespace_);


  const std::basic_string&lt;C>&amp;
  name () const;

  const std::basic_string&lt;C>&amp;
  namespace_ () const;


  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::expected_element</code> exception is thrown
     when an expected element is not encountered by the DOM-Tree stage.
     The name and namespace of the expected element can be obtained using
     the <code>name</code> and <code>namespace_</code> functions respectively.
  </p>


  <h3><a name="3.3.3">3.3.3 <code>xml_schema::unexpected_element</code></a></h3>

  <pre class="c++">
struct unexpected_element: virtual exception
{
  unexpected_element (const std::basic_string&lt;C>&amp; encountered_name,
                      const std::basic_string&lt;C>&amp; encountered_namespace,
                      const std::basic_string&lt;C>&amp; expected_name,
                      const std::basic_string&lt;C>&amp; expected_namespace)


  const std::basic_string&lt;C>&amp;
  encountered_name () const;

  const std::basic_string&lt;C>&amp;
  encountered_namespace () const;


  const std::basic_string&lt;C>&amp;
  expected_name () const;

  const std::basic_string&lt;C>&amp;
  expected_namespace () const;


  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::unexpected_element</code> exception is thrown
     when an unexpected element is encountered by the DOM-Tree stage.
     The name and namespace of the encountered element can be obtained
     using the <code>encountered_name</code> and
     <code>encountered_namespace</code> functions respectively. If an
     element was expected instead of the encountered one, its name
     and namespace can be obtained using the <code>expected_name</code> and
     <code>expected_namespace</code> functions respectively. Otherwise
     these functions return empty strings.
  </p>

  <h3><a name="3.3.4">3.3.4 <code>xml_schema::expected_attribute</code></a></h3>

  <pre class="c++">
struct expected_attribute: virtual exception
{
  expected_attribute (const std::basic_string&lt;C>&amp; name,
                      const std::basic_string&lt;C>&amp; namespace_);


  const std::basic_string&lt;C>&amp;
  name () const;

  const std::basic_string&lt;C>&amp;
  namespace_ () const;


  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::expected_attribute</code> exception is thrown
     when an expected attribute is not encountered by the DOM-Tree stage.
     The name and namespace of the expected attribute can be obtained using
     the <code>name</code> and <code>namespace_</code> functions respectively.
  </p>


  <h3><a name="3.3.5">3.3.5 <code>xml_schema::unexpected_enumerator</code></a></h3>

  <pre class="c++">
struct unexpected_enumerator: virtual exception
{
  unexpected_enumerator (const std::basic_string&lt;C>&amp; enumerator);

  const std::basic_string&lt;C>&amp;
  enumerator () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::unexpected_enumerator</code> exception is thrown
     when an unexpected enumerator is encountered by the DOM-Tree stage.
     The enumerator can be obtained using the <code>enumerator</code>
     functions.
  </p>

  <h3><a name="3.3.6">3.3.6 <code>xml_schema::expected_text_content</code></a></h3>

  <pre class="c++">
struct expected_text_content: virtual exception
{
  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::expected_text_content</code> exception is thrown
     when a content other than text is encountered and the text content was
     expected by the DOM-Tree stage.
  </p>

  <h3><a name="3.3.7">3.3.7 <code>xml_schema::no_type_info</code></a></h3>

  <pre class="c++">
struct no_type_info: virtual exception
{
  no_type_info (const std::basic_string&lt;C>&amp; type_name,
                const std::basic_string&lt;C>&amp; type_namespace);

  const std::basic_string&lt;C>&amp;
  type_name () const;

  const std::basic_string&lt;C>&amp;
  type_namespace () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::no_type_info</code> exception is thrown
     when there is no type information associated with a type specified
     by the <code>xsi:type</code> attribute. This exception is thrown
     by the DOM-Tree stage. The name and namespace of the type in question
     can be obtained using the <code>type_name</code> and
     <code>type_namespace</code> functions respectively. Usually, catching
     this exception means that you haven't linked the code generated
     from the schema defining the type in question with your application
     or this schema has been compiled without the
     <code>--generate-polymorphic</code> option.
  </p>


  <h3><a name="3.3.8">3.3.8 <code>xml_schema::not_derived</code></a></h3>

  <pre class="c++">
struct not_derived: virtual exception
{
  not_derived (const std::basic_string&lt;C>&amp; base_type_name,
               const std::basic_string&lt;C>&amp; base_type_namespace,
               const std::basic_string&lt;C>&amp; derived_type_name,
               const std::basic_string&lt;C>&amp; derived_type_namespace);

  const std::basic_string&lt;C>&amp;
  base_type_name () const;

  const std::basic_string&lt;C>&amp;
  base_type_namespace () const;


  const std::basic_string&lt;C>&amp;
  derived_type_name () const;

  const std::basic_string&lt;C>&amp;
  derived_type_namespace () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::not_derived</code> exception is thrown
     when a type specified by the <code>xsi:type</code> attribute is
     not derived from the expected base type. This exception is thrown
     by the DOM-Tree stage. The name and namespace of the expected
     base type can be obtained using the <code>base_type_name</code> and
     <code>base_type_namespace</code> functions respectively. The name
     and namespace of the offending type can be obtained using the
     <code>derived_type_name</code> and
     <code>derived_type_namespace</code> functions respectively.
  </p>

  <h3><a name="3.3.9">3.3.9 <code>xml_schema::no_prefix_mapping</code></a></h3>

  <pre class="c++">
struct no_prefix_mapping: virtual exception
{
  no_prefix_mapping (const std::basic_string&lt;C>&amp; prefix);

  const std::basic_string&lt;C>&amp;
  prefix () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::no_prefix_mapping</code> exception is thrown
     during the DOM-Tree stage if a namespace prefix is encountered for
     which a prefix-namespace mapping hasn't been provided. The namespace
     prefix in question can be obtained using the <code>prefix</code>
     function.
  </p>

  <h2><a name="3.4">3.4 Reading from a Local File or URI</a></h2>

  <p>Using a local file or URI is the simplest way to parse an XML instance.
     For example:</p>

  <pre class="c++">
using std::auto_ptr;

auto_ptr&lt;type> r1 (name ("test.xml"));
auto_ptr&lt;type> r2 (name ("https://www.codesynthesis.com/test.xml"));
  </pre>

  <p>Or, in the C++11 mode:</p>

  <pre class="c++">
using std::unique_ptr;

unique_ptr&lt;type> r1 (name ("test.xml"));
unique_ptr&lt;type> r2 (name ("https://www.codesynthesis.com/test.xml"));
  </pre>

  <h2><a name="3.5">3.5 Reading from <code>std::istream</code></a></h2>

  <p>When using an <code>std::istream</code> instance, you may also
     pass an optional resource id. This id is used to identify the
     resource (for example in error messages) as well as to resolve
     relative paths. For instance:</p>

  <pre class="c++">
using std::auto_ptr;

{
  std::ifstream ifs ("test.xml");
  auto_ptr&lt;type> r (name (ifs, "test.xml"));
}

{
  std::string str ("..."); // Some XML fragment.
  std::istringstream iss (str);
  auto_ptr&lt;type> r (name (iss));
}
  </pre>

  <h2><a name="3.6">3.6 Reading from <code>xercesc::InputSource</code></a></h2>

  <p>Reading from a <code>xercesc::InputSource</code> instance
     is similar to the <code>std::istream</code> case except
     the resource id is maintained by the <code>InputSource</code>
     object. For instance:</p>

  <pre class="c++">
xercesc::StdInInputSource is;
std::auto_ptr&lt;type> r (name (is));
  </pre>

  <h2><a name="3.7">3.7 Reading from DOM</a></h2>

  <p>Reading from a <code>xercesc::DOMDocument</code> instance allows
     you to setup a custom XML-DOM stage. Things like DOM
     parser reuse, schema pre-parsing, and schema caching can be achieved
     with this approach. For more information on how to obtain DOM
     representation from an XML instance refer to the Xerces-C++
     documentation. In addition, the
     <a href="http://wiki.codesynthesis.com/Tree/FAQ">C++/Tree Mapping
     FAQ</a> shows how to parse an XML instance to a Xerces-C++
     DOM document using the XSD runtime utilities.
  </p>

  <p>The last parsing function is useful when you would like to perform
     your own XML-to-DOM parsing and associate the resulting DOM document
     with the object model nodes. The automatic <code>DOMDocument</code>
     pointer is reset and the resulting object model assumes ownership
     of the DOM document passed. For example:</p>

  <pre class="c++">
// C++98 version.
//
xml_schema::dom::auto_ptr&lt;xercesc::DOMDocument> doc = ...

std::auto_ptr&lt;type> r (
  name (doc, xml_schema::flags::keep_dom | xml_schema::flags::own_dom));

// At this point doc is reset to 0.

// C++11 version.
//
xml_schema::dom::unique_ptr&lt;xercesc::DOMDocument> doc = ...

std::unique_ptr&lt;type> r (
  name (std::move (doc),
        xml_schema::flags::keep_dom | xml_schema::flags::own_dom));

// At this point doc is reset to 0.
  </pre>

  <h1><a name="4">4 Serialization</a></h1>

  <p>This chapter covers various aspects of serializing a
     tree-like object model to DOM or XML.
     In this regard, serialization is complimentary to the reverse
     process of parsing a DOM or XML instance into an object model
     which is discussed in <a href="#3">Chapter 3,
     "Parsing"</a>. Note that the generation of the serialization code
     is optional and should be explicitly requested with the
     <code>--generate-serialization</code> option. See the
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a> for more information.
  </p>

  <p>Each global XML Schema element in the form:
  </p>


  <pre class="xml">
&lt;xsd:element name="name" type="type"/>
  </pre>

  <p>is mapped to 8 overloaded C++ functions in the form:</p>

  <pre class="c++">
// Serialize to std::ostream.
//
void
name (std::ostream&amp;,
      const type&amp;,
      const xml_schema::namespace_fomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);

void
name (std::ostream&amp;,
      const type&amp;,
      xml_schema::error_handler&amp;,
      const xml_schema::namespace_infomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);

void
name (std::ostream&amp;,
      const type&amp;,
      xercesc::DOMErrorHandler&amp;,
      const xml_schema::namespace_infomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);


// Serialize to XMLFormatTarget.
//
void
name (xercesc::XMLFormatTarget&amp;,
      const type&amp;,
      const xml_schema::namespace_infomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);

void
name (xercesc::XMLFormatTarget&amp;,
      const type&amp;,
      xml_schema::error_handler&amp;,
      const xml_schema::namespace_infomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);

void
name (xercesc::XMLFormatTarget&amp;,
      const type&amp;,
      xercesc::DOMErrorHandler&amp;,
      const xml_schema::namespace_infomap&amp; =
        xml_schema::namespace_infomap (),
      const std::basic_string&lt;C>&amp; encoding = "UTF-8",
      xml_schema::flags = 0);


// Serialize to DOM.
//
xml_schema::dom::[auto|unique]_ptr&lt;xercesc::DOMDocument>
name (const type&amp;,
      const xml_schema::namespace_infomap&amp;
        xml_schema::namespace_infomap (),
      xml_schema::flags = 0);

void
name (xercesc::DOMDocument&amp;,
      const type&amp;,
      xml_schema::flags = 0);
  </pre>

  <p>You can choose between writing XML to <code>std::ostream</code> or
     <code>xercesc::XMLFormatTarget</code> and creating a DOM instance
     in the form of <code>xercesc::DOMDocument</code>. Serialization
     to <code>ostream</code> or <code>XMLFormatTarget</code> requires a
     considerably less work while serialization to DOM provides
     for greater flexibility. Each of these serialization functions
     is discussed in more detail in the following sections.
  </p>


  <h2><a name="4.1">4.1 Initializing the Xerces-C++ Runtime</a></h2>

  <p>Some serialization functions expect you to initialize the Xerces-C++
     runtime while others initialize and terminate it as part of their
     work. The general rule is as follows: if a function has any arguments
     or return a value that is an instance of a Xerces-C++ type, then
     this function expects you to initialize the Xerces-C++ runtime.
     Otherwise, the function initializes and terminates the runtime for
     you. Note that it is legal to have nested calls to the Xerces-C++
     initialize and terminate functions as long as the calls are balanced.
  </p>

  <p>You can instruct serialization functions that initialize and terminate
     the runtime not to do so by passing the
     <code>xml_schema::flags::dont_initialize</code> flag (see
     <a href="#4.3">Section 4.3, "Flags"</a>).
  </p>

  <h2><a name="4.2">4.2 Namespace Infomap and Character Encoding</a></h2>

  <p>When a document being serialized uses XML namespaces, custom
     prefix-namespace associations can to be established. If custom
     prefix-namespace mapping is not provided then generic prefixes
     (<code>p1</code>, <code>p2</code>, etc) are automatically assigned
     to namespaces as needed. Also, if
     you would like the resulting instance document to contain the
     <code>schemaLocation</code> or <code>noNamespaceSchemaLocation</code>
     attributes, you will need to provide namespace-schema associations.
     The <code>xml_schema::namespace_infomap</code> class is used
     to capture this information:</p>

  <pre class="c++">
struct namespace_info
{
  namespace_info ();
  namespace_info (const std::basic_string&lt;C>&amp; name,
                  const std::basic_string&lt;C>&amp; schema);

  std::basic_string&lt;C> name;
  std::basic_string&lt;C> schema;
};

// Map of namespace prefix to namespace_info.
//
struct namespace_infomap: public std::map&lt;std::basic_string&lt;C>,
                                          namespace_info>
{
};
  </pre>

  <p>Consider the following associations as an example:</p>

  <pre class="c++">
xml_schema::namespace_infomap map;

map["t"].name = "https://www.codesynthesis.com/test";
map["t"].schema = "test.xsd";
  </pre>

  <p>This map, if passed to one of the serialization functions,
     could result in the following XML fragment:</p>

  <pre class="xml">
&lt;?xml version="1.0" ?>
&lt;t:name xmlns:t="https://www.codesynthesis.com/test"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="https://www.codesynthesis.com/test test.xsd">
  </pre>

  <p>As you can see, the serialization function automatically added namespace
     mapping for the <code>xsi</code> prefix. You can change this by
     providing your own prefix:</p>

  <pre class="c++">
xml_schema::namespace_infomap map;

map["xsn"].name = "http://www.w3.org/2001/XMLSchema-instance";

map["t"].name = "https://www.codesynthesis.com/test";
map["t"].schema = "test.xsd";
  </pre>

  <p>This could result in the following XML fragment:</p>

  <pre class="xml">
&lt;?xml version="1.0" ?>
&lt;t:name xmlns:t="https://www.codesynthesis.com/test"
        xmlns:xsn="http://www.w3.org/2001/XMLSchema-instance"
        xsn:schemaLocation="https://www.codesynthesis.com/test test.xsd">
  </pre>

  <p>To specify the location of a schema without a namespace you can use
     an empty prefix as in the example below: </p>

  <pre class="c++">
xml_schema::namespace_infomap map;

map[""].schema = "test.xsd";
  </pre>

  <p>This would result in the following XML fragment:</p>

  <pre class="xml">
&lt;?xml version="1.0" ?>
&lt;name xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:noNamespaceSchemaLocation="test.xsd">
  </pre>

  <p>To make a particular namespace default you can use an empty
     prefix, for example:</p>

  <pre class="c++">
xml_schema::namespace_infomap map;

map[""].name = "https://www.codesynthesis.com/test";
map[""].schema = "test.xsd";
  </pre>

  <p>This could result in the following XML fragment:</p>

  <pre class="xml">
&lt;?xml version="1.0" ?>
&lt;name xmlns="https://www.codesynthesis.com/test"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="https://www.codesynthesis.com/test test.xsd">
  </pre>


  <p>Another bit of information that you can pass to the serialization
     functions is the character encoding method that you would like to use.
     Common values for this argument are <code>"US-ASCII"</code>,
     <code>"ISO8859-1"</code>, <code>"UTF-8"</code>,
     <code>"UTF-16BE"</code>, <code>"UTF-16LE"</code>,
     <code>"UCS-4BE"</code>, and <code>"UCS-4LE"</code>. The default
     encoding is <code>"UTF-8"</code>. For more information on
     encoding methods see the
     "<a href="http://en.wikipedia.org/wiki/Character_code">Character
     Encoding</a>" article from Wikipedia.
  </p>

  <h2><a name="4.3">4.3 Flags</a></h2>

  <p>Serialization flags are the last argument of every serialization
     function. They allow you to fine-tune the process of serialization.
     The flags argument is optional.
  </p>


  <p>The following flags are recognized by the serialization
     functions:</p>

  <dl>
    <dt><code>xml_schema::flags::dont_initialize</code></dt>
    <dd>Do not initialize the Xerces-C++ runtime.</dd>

    <dt><code>xml_schema::flags::dont_pretty_print</code></dt>
    <dd>Do not add extra spaces or new lines that make the resulting XML
        slightly bigger but easier to read.</dd>

    <dt><code>xml_schema::flags::no_xml_declaration</code></dt>
    <dd>Do not write XML declaration (&lt;?xml ... ?>).</dd>
  </dl>

  <p>You can pass several flags by combining them using the bit-wise OR
     operator. For example:</p>

  <pre class="c++">
std::auto_ptr&lt;type> r = ...
std::ofstream ofs ("test.xml");
xml_schema::namespace_infomap map;
name (ofs,
      *r,
      map,
      "UTF-8",
      xml_schema::flags::no_xml_declaration |
      xml_schema::flags::dont_pretty_print);
  </pre>

  <p>For more information on the Xerces-C++ runtime initialization
     refer to <a href="#4.1">Section 4.1, "Initializing the Xerces-C++
     Runtime"</a>.
  </p>

  <h2><a name="4.4">4.4 Error Handling</a></h2>

  <p>As with the parsing functions (see <a href="#3.3">Section 3.3,
     "Error Handling"</a>), to better understand error handling and
     reporting strategies employed by the serialization functions, it
     is useful to know that the transformation of a statically-typed
     tree to an XML instance document happens in two stages. The first
     stage, performed by the generated code, consist of building a DOM
     instance from the statically-typed tree . For short, we will call
     this stage the Tree-DOM stage. The second stage, performed by
     Xerces-C++, consists of serializing the DOM instance into the XML
     document. We will call this stage the DOM-XML stage.
  </p>

  <p>All serialization functions except the two that serialize into
     a DOM instance come in overloaded triples. The first function
     in such a triple reports error conditions exclusively by throwing
     exceptions. It accumulates all the serialization errors of the
     DOM-XML stage and throws them in a single instance of the
     <code>xml_schema::serialization</code> exception (described below).
     The second and the third functions in the triple use callback
     interfaces to report serialization errors and warnings. The two
     callback interfaces are <code>xml_schema::error_handler</code> and
     <code>xercesc::DOMErrorHandler</code>. The
     <code>xml_schema::error_handler</code> interface is described in
     <a href="#3.3">Section 3.3, "Error Handling"</a>. For more information
     on the <code>xercesc::DOMErrorHandler</code> interface refer to the
     Xerces-C++ documentation.
  </p>

  <p>The Tree-DOM stage reports error conditions exclusively by throwing
     exceptions. Individual exceptions thrown by the serialization functions
     are described in the following sub-sections.
  </p>

  <h3><a name="4.4.1">4.4.1 <code>xml_schema::serialization</code></a></h3>

  <pre class="c++">
struct serialization: virtual exception
{
  serialization ();
  serialization (const diagnostics&amp;);

  const diagnostics&amp;
  diagnostics () const;

  virtual const char*
  what () const throw ();
};
  </pre>

  <p>The <code>xml_schema::diagnostics</code> class is described in
     <a href="#3.3.1">Section 3.3.1, "<code>xml_schema::parsing</code>"</a>.
     The <code>xml_schema::serialization</code> exception is thrown if
     there were serialization errors reported during the DOM-XML stage.
     If no callback interface was provided to the serialization function,
     the exception contains a list of errors and warnings accessible using
     the <code>diagnostics</code> function.
  </p>


  <h3><a name="4.4.2">4.4.2 <code>xml_schema::unexpected_element</code></a></h3>

  <p>The <code>xml_schema::unexpected_element</code> exception is
     described in <a href="#3.3.3">Section 3.3.3,
     "<code>xml_schema::unexpected_element</code>"</a>. It is thrown
     by the serialization functions during the Tree-DOM stage if the
     root element name of the provided DOM instance does not match with
     the name of the element this serialization function is for.
  </p>

  <h3><a name="4.4.3">4.4.3 <code>xml_schema::no_type_info</code></a></h3>

  <p>The <code>xml_schema::no_type_info</code> exception is
     described in <a href="#3.3.7">Section 3.3.7,
     "<code>xml_schema::no_type_info</code>"</a>. It is thrown
     by the serialization functions during the Tree-DOM stage when there
     is no type information associated with a dynamic type of an
     element. Usually, catching this exception means that you haven't
     linked the code generated from the schema defining the type in
     question with your application or this schema has been compiled
     without the <code>--generate-polymorphic</code> option.
  </p>

  <h2><a name="4.5">4.5 Serializing to <code>std::ostream</code></a></h2>

  <p>In order to serialize to <code>std::ostream</code> you will need
     an object model, an output stream and, optionally, a namespace
     infomap. For instance:</p>

  <pre class="c++">
// Obtain the object model.
//
std::auto_ptr&lt;type> r = ...

// Prepare namespace mapping and schema location information.
//
xml_schema::namespace_infomap map;

map["t"].name = "https://www.codesynthesis.com/test";
map["t"].schema = "test.xsd";

// Write it out.
//
name (std::cout, *r, map);
  </pre>

  <p>Note that the output stream is treated as a binary stream. This
     becomes important when you use a character encoding that is wider
     than 8-bit <code>char</code>, for instance UTF-16 or UCS-4. For
     example, things will most likely break if you try to serialize
     to <code>std::ostringstream</code> with UTF-16 or UCS-4 as an
     encoding. This is due to the special value,
     <code>'\0'</code>, that will most likely occur as part of such
     serialization and it won't have the special meaning assumed by
     <code>std::ostringstream</code>.
  </p>


  <h2><a name="4.6">4.6 Serializing to <code>xercesc::XMLFormatTarget</code></a></h2>

  <p>Serializing to an <code>xercesc::XMLFormatTarget</code> instance
     is similar the <code>std::ostream</code> case. For instance:
  </p>

  <pre class="c++">
using std::auto_ptr;

// Obtain the object model.
//
auto_ptr&lt;type> r = ...

// Prepare namespace mapping and schema location information.
//
xml_schema::namespace_infomap map;

map["t"].name = "https://www.codesynthesis.com/test";
map["t"].schema = "test.xsd";

using namespace xercesc;

XMLPlatformUtils::Initialize ();

{
  // Choose a target.
  //
  auto_ptr&lt;XMLFormatTarget> ft;

  if (argc != 2)
  {
    ft = auto_ptr&lt;XMLFormatTarget> (new StdOutFormatTarget ());
  }
  else
  {
    ft = auto_ptr&lt;XMLFormatTarget> (
      new LocalFileFormatTarget (argv[1]));
  }

  // Write it out.
  //
  name (*ft, *r, map);
}

XMLPlatformUtils::Terminate ();
  </pre>

  <p>Note that we had to initialize the Xerces-C++ runtime before we
     could call this serialization function.</p>

  <h2><a name="4.7">4.7 Serializing to DOM</a></h2>

  <p>The mapping provides two overloaded functions that implement
     serialization to a DOM instance. The first creates a DOM instance
     for you and the second serializes to an existing DOM instance.
     While serializing to a new DOM instance is similar to serializing
     to <code>std::ostream</code> or <code>xercesc::XMLFormatTarget</code>,
     serializing to an existing DOM instance requires quite a bit of work
     from your side. You will need to set all the custom namespace mapping
     attributes as well as the <code>schemaLocation</code> and/or
     <code>noNamespaceSchemaLocation</code> attributes. The following
     listing should give you an idea about what needs to be done:
  </p>

  <pre class="c++">
// Obtain the object model.
//
std::auto_ptr&lt;type> r = ...

using namespace xercesc;

XMLPlatformUtils::Initialize ();

{
  // Create a DOM instance. Set custom namespace mapping and schema
  // location attributes.
  //
  DOMDocument&amp; doc = ...

  // Serialize to DOM.
  //
  name (doc, *r);

  // Serialize the DOM document to XML.
  //
  ...
}

XMLPlatformUtils::Terminate ();
  </pre>

  <p>For more information on how to create and serialize a DOM instance
     refer to the Xerces-C++ documentation. In addition, the
     <a href="http://wiki.codesynthesis.com/Tree/FAQ">C++/Tree Mapping
     FAQ</a> shows how to implement these operations using the XSD
     runtime utilities.
  </p>

  <h1><a name="5">5 Additional Functionality</a></h1>

  <p>The C++/Tree mapping provides a number of optional features
     that can be useful in certain situations. They are described
     in the following sections.</p>

  <h2><a name="5.1">5.1 DOM Association</a></h2>

  <p>Normally, after parsing is complete, the DOM document which
     was used to extract the data is discarded. However, the parsing
     functions can be instructed to preserve the DOM document
     and create an association between the DOM nodes and object model
     nodes. When there is an association between the DOM and
     object model nodes, you can obtain the corresponding DOM element
     or attribute node from an object model node as well as perform
     the reverse transition: obtain the corresponding object model
     from a DOM element or attribute node.</p>

  <p>Maintaining DOM association is normally useful when the application
     needs access to XML constructs that are not preserved in the
     object model, for example, XML comments.
     Another useful aspect of DOM association is the ability of the
     application to navigate the document tree using the generic DOM
     interface (for example, with the help of an XPath processor)
     and then move back to the statically-typed object model. Note
     also that while you can change the underlying DOM document,
     these changes are not reflected in the object model and will
     be ignored during serialization. If you need to not only access
     but also modify some aspects of XML that are not preserved in
     the object model, then type customization with custom parsing
     constructors and serialization operators should be used instead.</p>

  <p>To request DOM association you will need to pass the
     <code>xml_schema::flags::keep_dom</code> flag to one of the
     parsing functions (see <a href="#3.2">Section 3.2,
     "Flags and Properties"</a> for more information). In this case the
     DOM document is retained and will be released when the object model
     is deleted. Note that since DOM nodes "out-live" the parsing function
     call, you need to initialize the Xerces-C++ runtime before calling
     one of the parsing functions with the <code>keep_dom</code> flag and
     terminate it after the object model is destroyed (see
     <a href="#3.1">Section 3.1, "Initializing the Xerces-C++ Runtime"</a>).</p>

   <p>If the <code>keep_dom</code> flag is passed
      as the second argument to the copy constructor and the copy
      being made is of a complete tree, then the DOM association
      is also maintained in the copy by cloning the underlying
      DOM document and reestablishing the associations. For example:</p>

  <pre class="c++">
using namespace xercesc;

XMLPlatformUtils::Initialize ();

{
  // Parse XML to object model.
  //
  std::auto_ptr&lt;type> r (root (
    "root.xml",
     xml_schema::flags::keep_dom |
     xml_schema::flags::dont_initialize));

   // Copy without DOM association.
   //
   type copy1 (*r);

   // Copy with DOM association.
   //
   type copy2 (*r, xml_schema::flags::keep_dom);
}

XMLPlatformUtils::Terminate ();
  </pre>


  <p>To obtain the corresponding DOM node from an object model node
     you will need to call the <code>_node</code> accessor function
     which returns a pointer to <code>DOMNode</code>. You can then query
     this DOM node's type and cast it to either <code>DOMAttr*</code>
     or <code>DOMElement*</code>. To obtain the corresponding object
     model node from a DOM node, the DOM user data API is used. The
     <code>xml_schema::dom::tree_node_key</code> variable contains
     the key for object model nodes. The following schema and code
     fragment show how to navigate from DOM to object model nodes
     and in the opposite direction:</p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="a" type="string"/>
  &lt;/sequence>
&lt;/complexType>

&lt;element name="root" type="object"/>
  </pre>

  <pre class="c++">
using namespace xercesc;

XMLPlatformUtils::Initialize ();

{
  // Parse XML to object model.
  //
  std::auto_ptr&lt;type> r (root (
    "root.xml",
     xml_schema::flags::keep_dom |
     xml_schema::flags::dont_initialize));

  DOMNode* n = r->_node ();
  assert (n->getNodeType () == DOMNode::ELEMENT_NODE);
  DOMElement* re = static_cast&lt;DOMElement*> (n);

  // Get the 'a' element. Note that it is not necessarily the
  // first child node of 'root' since there could be whitespace
  // nodes before it.
  //
  DOMElement* ae;

  for (n = re->getFirstChild (); n != 0; n = n->getNextSibling ())
  {
    if (n->getNodeType () == DOMNode::ELEMENT_NODE)
    {
      ae = static_cast&lt;DOMElement*> (n);
      break;
    }
  }

  // Get from the 'a' DOM element to xml_schema::string object model
  // node.
  //
  xml_schema::type&amp; t (
    *reinterpret_cast&lt;xml_schema::type*> (
       ae->getUserData (xml_schema::dom::tree_node_key)));

  xml_schema::string&amp; a (dynamic_cast&lt;xml_schema::string&amp;> (t));
}

XMLPlatformUtils::Terminate ();
  </pre>

  <p>The 'mixed' example which can be found in the XSD distribution
     shows how to handle the mixed content using DOM association.</p>

  <h2><a name="5.2">5.2 Binary Serialization</a></h2>

  <p>Besides reading from and writing to XML, the C++/Tree mapping
     also allows you to save the object model to and load it from a
     number of predefined as well as custom data representation
     formats. The predefined binary formats are CDR (Common Data
     Representation) and XDR (eXternal Data Representation). A
     custom format can easily be supported by providing
     insertion and extraction operators for basic types.</p>

  <p>Binary serialization saves only the data without any meta
     information or markup. As a result, saving to and loading
     from a binary representation can be an order of magnitude
     faster than parsing and serializing the same data in XML.
     Furthermore, the resulting representation is normally several
     times smaller than the equivalent XML representation. These
     properties make binary serialization ideal for internal data
     exchange and storage. A typical application that uses this
     facility stores the data and communicates within the
     system using a binary format and reads/writes the data
     in XML when communicating with the outside world.</p>

  <p>In order to request the generation of insertion operators and
     extraction constructors for a specific predefined or custom
     data representation stream, you will need to use the
     <code>--generate-insertion</code> and <code>--generate-extraction</code>
     compiler options. See the
     <a href="https://www.codesynthesis.com/projects/xsd/documentation/xsd.xhtml">XSD
     Compiler Command Line Manual</a> for more information.</p>

  <p>Once the insertion operators and extraction constructors are
     generated, you can use the <code>xml_schema::istream</code>
     and <code>xml_schema::ostream</code> wrapper stream templates
     to save the object model to and load it from a specific format.
     The following code fragment shows how to do this using ACE
     (Adaptive Communication Environment) CDR streams as an example:</p>

  <pre class="xml">
&lt;complexType name="object">
  &lt;sequence>
    &lt;element name="a" type="string"/>
    &lt;element name="b" type="int"/>
  &lt;/sequence>
&lt;/complexType>

&lt;element name="root" type="object"/>
  </pre>

  <pre class="c++">
// Parse XML to object model.
//
std::auto_ptr&lt;type> r (root ("root.xml"));

// Save to a CDR stream.
//
ACE_OutputCDR ace_ocdr;
xml_schema::ostream&lt;ACE_OutputCDR> ocdr (ace_ocdr);

ocdr &lt;&lt; *r;

// Load from a CDR stream.
//
ACE_InputCDR ace_icdr (buf, size);
xml_schema::istream&lt;ACE_InputCDR> icdr (ace_icdr);

std::auto_ptr&lt;object> copy (new object (icdr));

// Serialize to XML.
//
root (std::cout, *copy);
  </pre>

  <p>The XSD distribution contains a number of examples that
     show how to save the object model to and load it from
     CDR, XDR, and a custom format.</p>

  <!--  Appendix A -->


  <h1><a name="A">Appendix A &mdash; Default and Fixed Values</a></h1>

  <p>The following table summarizes the effect of default and fixed
     values (specified with the <code>default</code> and <code>fixed</code>
     attributes, respectively) on attribute and element values. The
     <code>default</code> and <code>fixed</code> attributes are mutually
     exclusive. It is also worthwhile to note that the fixed value semantics
     is a superset of the default value semantics.
  </p>

  <!-- border="1" is necessary for html2ps -->
  <table id="default-fixed" border="1">
    <tr>
      <th></th>
      <th></th>
      <th colspan="2">default</th>
      <th colspan="2">fixed</th>
    </tr>

    <!-- element -->

    <tr>
      <th rowspan="4">element</th>
      <th rowspan="2">not present</th>
      <th>optional</th>
      <th>required</th>
      <th>optional</th>
      <th>required</th>
    </tr>
    <tr>
      <td>not present</td>
      <td>invalid instance</td>
      <td>not present</td>
      <td>invalid instance</td>
    </tr>


    <tr>
      <th>empty</th>
      <td colspan="2">default value is used</td>
      <td colspan="2">fixed value is used</td>
    </tr>

    <tr>
      <th>value</th>
      <td colspan="2">value is used</td>
      <td colspan="2">value is used provided it's the same as fixed</td>
    </tr>

    <!-- attribute -->

    <!-- element -->

    <tr>
      <th rowspan="4">attribute</th>
      <th rowspan="2">not present</th>
      <th>optional</th>
      <th>required</th>
      <th>optional</th>
      <th>required</th>
    </tr>
    <tr>
      <td>default value is used</td>
      <td>invalid schema</td>
      <td>fixed value is used</td>
      <td>invalid instance</td>
    </tr>


    <tr>
      <th>empty</th>
      <td colspan="2">empty value is used</td>
      <td colspan="2">empty value is used provided it's the same as fixed</td>
    </tr>

    <tr>
      <th>value</th>
      <td colspan="2">value is used</td>
      <td colspan="2">value is used provided it's the same as fixed</td>
    </tr>

  </table>

  </div>
</div>


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</html>