public Collection<? extends NetworkNode> getSinkList() {
if ( node instanceof Rete ) {
Rete rete = (Rete) node;
return rete.getEntryPointNodes().values();
} else if ( node instanceof EntryPointNode ) {
EntryPointNode epn = (EntryPointNode) node;
return epn.getObjectTypeNodes().values();
} else if ( node instanceof ObjectSource ) {
List<NetworkNode> result = new ArrayList<NetworkNode>();
for ( ObjectSink sink : ((ObjectSource)node).getSinkPropagator().getSinks() ) {
result.add( (NetworkNode) sink );
}