1 files changed, 52 insertions, 1 deletions

diff --git a/odb/semantics/relational/changeset.hxx b/odb/semantics/relational/changeset.hxx
index 76fd683..27c80fe 100644
--- a/odb/semantics/relational/changeset.hxx
+++ b/odb/semantics/relational/changeset.hxx
@@ -11,6 +11,43 @@ namespace semantics
 {
   namespace relational
   {
+    class model;
+    class changeset;
+
+    class alters_model: public edge
+    {
+    public:
+      typedef relational::model model_type;
+      typedef relational::changeset changeset_type;
+
+      model_type&
+      model () const {return *model_;}
+
+      changeset_type&
+      changeset () const {return *changeset_;}
+
+    public:
+      alters_model () : model_ (0), changeset_ (0) {}
+
+      void
+      set_left_node (changeset_type& c)
+      {
+        assert (changeset_ == 0);
+        changeset_ = &c;
+      }
+
+      void
+      set_right_node (model_type& m)
+      {
+        assert (model_ == 0);
+        model_ = &m;
+      }
+
+    protected:
+      model_type* model_;
+      changeset_type* changeset_;
+    };
+
     class changeset: public qscope
     {
     public:
@@ -19,8 +56,14 @@ namespace semantics
       version_type
       version () const {return version_;}
 
+      // Returns model to which this changeset applies (as opposed to the
+      // ultimate base model). Note that it may not be set.
+      //
+      model&
+      base_model () const {return alters_model_->model ();}
+
     public:
-      changeset (version_type v): version_ (v) {}
+      changeset (version_type v): version_ (v), alters_model_ (0) {}
       changeset (changeset const&, qscope& base, graph&);
       changeset (xml::parser&, qscope& base, graph&);
 
@@ -31,11 +74,19 @@ namespace semantics
       serialize (xml::serializer&) const;
 
     public:
+      virtual void
+      add_edge_left (alters_model& am)
+      {
+        assert (alters_model_ == 0);
+        alters_model_ = &am;
+      }
+
       using qscope::add_edge_left;
       using qscope::add_edge_right;
 
     private:
       version_type version_;
+      alters_model* alters_model_;
     };
   }
 }