}
// first, iterate over all elements capable of defining an extends attribute
// collecting all found extends references if they cannot be resolved
// against the already processed mappings.
subclasses[0] = hmNode.elementIterator( "subclass" );
subclasses[1] = hmNode.elementIterator( "joined-subclass" );
subclasses[2] = hmNode.elementIterator( "union-subclass" );
Iterator iterator = new JoinedIterator( subclasses );
while ( iterator.hasNext() ) {