@Override public Graph getGraph(Node graphNode) { if ( namedGraphs.containsKey(graphNode) ) { if ( ! super.containsGraph(graphNode) ) { namedGraphs.remove(graphNode) ; return null ; } return namedGraphs.get(graphNode) ; } Graph g = super.getGraph(graphNode) ; if ( g == null ) return null ; g = new GraphReadOnly(g) ; namedGraphs.put(graphNode, g) ; return g ; }