private void PopulateRelationStructure (string parent, string child, string pkeyColumn)
{
if (relations [parent, child] != null)
return;
RelationStructure rs = new RelationStructure ();
rs.ParentTableName = parent;
rs.ChildTableName = child;
rs.ParentColumnName = pkeyColumn;
rs.ChildColumnName = pkeyColumn;
rs.CreateConstraint = true;
rs.IsNested = true;
relations.Add (rs);
}