Convert an EasyRdf object into a GraphViz node identifier
@ignore
protected function nodeName($entity) {
if ($entity instanceof EasyRdf_Resource) {
if ($entity
->isBnode()) {
return "B" . $entity
->getUri();
}
else {
return "R" . $entity
->getUri();
}
}
else {
return "L" . $entity;
}
}