/**
* Build the condition (WHERE) string for a given Condition.
* The function also expresses the single value of
* SingletonCondition objects in the condition, which may
* lead to additional namespaces for serializing its URI.
*
* @param Condition $condition
*
* @return string
*/
public function convertConditionToString(Condition &$condition)
{
$conditionAsString = $condition->getWeakConditionString();
if ($conditionAsString === '' && !$condition->isSafe()) {
$swivtPageResource = Exporter::getInstance()->getSpecialNsResource('swivt', 'page');
$conditionAsString = '?' . $this->resultVariable . ' ' . $swivtPageResource->getQName() . " ?url .\n";
}
$conditionAsString .= $condition->getCondition();
if ($condition instanceof SingletonCondition) {
// prepare for ASK, maybe rather use BIND?
$matchElement = $condition->matchElement;
if ($matchElement instanceof ExpElement) {
$matchElementName = TurtleSerializer::getTurtleNameForExpElement($matchElement);
} else {
$matchElementName = $matchElement;
}
if ($matchElement instanceof ExpNsResource) {
$condition->namespaces[$matchElement->getNamespaceId()] = $matchElement->getNamespace();
}
$conditionAsString = str_replace('?' . $this->resultVariable . ' ', "{$matchElementName} ", $conditionAsString);
}
return $conditionAsString;
}
/**
* @see https://www.w3.org/TR/rdf-sparql-query/#func-bound
*
* Remove entities that contain a "swivt:redirectsTo" predicate
*/
private function addFilterToRemoveEntitiesThatContainRedirectPredicate(Condition &$condition)
{
$rediExpElement = Exporter::getInstance()->getSpecialPropertyResource('_REDI');
$namespaces[$rediExpElement->getNamespaceId()] = $rediExpElement->getNamespace();
$boundVariable = '?' . $this->getNextVariable('o');
$cogentCondition = " OPTIONAL { ?{$this->resultVariable} " . $rediExpElement->getQName() . " {$boundVariable} } .\n FILTER ( !bound( {$boundVariable} ) ) .\n";
$condition->addNamespaces($namespaces);
$condition->cogentConditions[$boundVariable] = $cogentCondition;
}