             return _rootNode;
         }
 
-
-
-        override public function getAttributeColumn(metadata:Object):IAttributeColumn
-        {
-            return null;
-        }
-
         /* Local logic */
 
         private function handleNodeLayeringChange():void

        if (children == null)
        {
            children = [];
            var columns:Array = group.isNodeGroup() ? group.graph.source.nodeProperties : group.graph.source.edgeProperties;

            for (var idx:int = columns.length - 1; idx >= 0; idx--)
            {

    import weave.core.LinkableVariable;
    import weave.core.SessionManager;
    import weave.data.AttributeColumns.ProxyColumn;
    import weave.data.AttributeColumns.StringColumn;
    import weave.data.AttributeColumns.NumberColumn;
    import weave.data.AttributeColumns.DateColumn;
    import weave.data.QKeyManager;
    import weave.core.ClassUtils;

    import weave.utils.VectorUtils;

    public class GraphMLDataSource extends AbstractDataSource
    {
        WeaveAPI.registerImplementation(IDataSource, GraphMLDataSource, "GraphML file");

        
        public static const COLUMNNAME_META:String = "__GraphElementProperty__";
        public static const FILTERVALUE_META:String = "__GraphFilterValue__";
        public static const FILTERCOLUMN_META:String = "__GraphFilterColumn__";
        public static const GROUP_META:String = "__GraphGroup__";

        public const nodeColumnData:LinkableVariable = newLinkableChild(this, LinkableVariable, handleGraphMLNodesChange);
        public const edgeColumnData:LinkableVariable = newLinkableChild(this, LinkableVariable, handleGraphMLEdgesChange);

        public const nodeProperties:LinkableVariable = newLinkableChild(this, LinkableVariable, handleGraphMLNodesChange);
        public const edgeProperties:LinkableVariable = newLinkableChild(this, LinkableVariable, handleGraphMLEdgesChange);

        public const nodeKeyType:LinkableString = newLinkableChild(this, LinkableString);
        public const edgeKeyType:LinkableString = newLinkableChild(this, LinkableString);

        public const nodeKeyPropertyName:LinkableString = newLinkableChild(this, LinkableString, handleNodeKeyPropertyChange);
        public const edgeKeyPropertyName:LinkableString = newLinkableChild(this, LinkableString, handleEdgeKeyPropertyChange);
