private function tryToAddClassHierarchyPattern($category, &$categoryExpName)
{
if (!$this->compoundConditionBuilder->canUseQFeature(SMW_SPARQL_QF_SUBC)) {
return '';
}
if ($this->compoundConditionBuilder->getPropertyHierarchyExaminer() === null || !$this->compoundConditionBuilder->getPropertyHierarchyExaminer()->hasSubcategoryFor($category)) {
return '';
}
$subClassExpElement = $this->exporter->getSpecialPropertyResource('_SUBC');
$classHierarchyByVariable = "?" . $this->compoundConditionBuilder->getNextVariable('sc');
$condition = "{$classHierarchyByVariable} " . $subClassExpElement->getQName() . "*" . " {$categoryExpName} .\n";
$categoryExpName = "{$classHierarchyByVariable}";
return $condition;
}