Table of Contents

• 1. Introduction
• 2. Don't define a global element which is not a valid document root
• 3. Don't name a type and an element/attribute of this type with the same name
• 3. Don't use xsd:integer and friends
• 4. Use xsd:int/xsd:unsignedInt for 32 bit integers

Introduction

Making it possible to cleanly map W3C XML Schema to programming languages was never a goal of the XML Schema Working Group. As a result there is a number of Schema constructs, techniques, and styles that don't have appropriate counterparts in C++. This document presents a list of do's and don'ts that will help ensure your schemas, when translated by XSD, result in C++ code that is enjoyable to work with.

Don't define a global element which is not a valid document root

Instead of

<xsd:element name="author" type="Author"/>

<xsd:complexType name="Book">
  <xsd:sequence>
    <xsd:element ref="author"/>
  </xsd:sequence>
</xsd:complexType>
  

Write

<xsd:complexType name="Book">
  <xsd:sequence>
    <xsd:element name="author" type="Author"/>
  </xsd:sequence>
</xsd:complexType>
  

Any globally-defined element is a potential document root. For every such element XSD generates a set of overloaded parsing functions. If you cannot change your schema, consider using the --root-element-* options to specify which global element(s) are actual document root(s).

Don't name a type and an element/attribute of this type with the same name

Instead of

<xsd:complexType name="name">
  <xsd:sequence>
    <xsd:element name="name" type="xsd:string"/>
  </xsd:sequence>
  <xsd:attribute name="lang" type="xsd:language"/>
</xsd:complexType>
  

Write

<xsd:complexType name="Name">
  <xsd:sequence>
    <xsd:element name="name" type="xsd:string"/>
  </xsd:sequence>
  <xsd:attribute name="lang" type="xsd:language"/>
</xsd:complexType>
  

Use of a class name as a member function name within this class is illegal in C++. XSD will resolve such conflicts by renaming the conflicting member function. In the example above, you will end up with the following generated code:

  class name
  {
  public:
    string
    name1 () const;

    language
    lang () const;

    ...

  };
  

Don't use xsd:integer and friends

XML Schema built-in types integer, nonPositiveInteger, nonNegativeInteger, positiveInteger, and negativeInteger are arbitrary-length integral types. XSD maps them to the long long and unsigned long long C++ types. In most cases you would prefer to use either xsd:int/xsd:unsignedInt (32 bit, maps to C++ int/unsigned int) or xsd:long/xsd:unsignedLong (64 bit, maps to C++ long long/unsigned long long).

Use xsd:int/xsd:unsignedInt for 32 bit integers

XML Schema built-in types long and unsignedLong are 64 bit wide so use 32 bit int and unsignedInt unless you meant 64 bit.