/**
* Creates a value node for $value, and attaches it to the current subject of $writer.
* If a value node for $value was already created, null is returned. Otherwise, the
* value node's lname is returned, which should be used to generate detailed about the
* value into the writer returned by getValueNodeWriter().
*
* When this method returns a non-null lname, the current subject of the RdfWriter returned by
* getValueNodeWriter() will the be value node with that lname.
*
* @param RdfWriter $writer
* @param string $propertyValueNamespace Property value relation namespace
* @param string $propertyValueLName Property value relation name
* @param string $dataType Property data type (unused, passed here for symmetry
* with the signature of ValueSnakRdfBuilder::addValue).
* @param DataValue $value
*
* @return string|null The LName of the value node (in the RdfVocabulary::NS_VALUE namespace),
* or null if the value node should not be processed (generally, because it already has
* been processed).
*/
public function attachValueNode(RdfWriter $writer, $propertyValueNamespace, $propertyValueLName, $dataType, DataValue $value)
{
$valueLName = $value->getHash();
$writer->say(RdfVocabulary::$claimToValue[$propertyValueNamespace], $propertyValueLName)->is(RdfVocabulary::NS_VALUE, $valueLName);
if ($this->dedupeBag->alreadySeen($valueLName, 'V') !== false) {
return null;
}
$this->valueNodeWriter->about(RdfVocabulary::NS_VALUE, $valueLName)->a(RdfVocabulary::NS_ONTOLOGY, $this->vocabulary->getValueTypeName($value));
return $valueLName;
}
