/**
* This implementation of the CrosswalkFilter
* simply removes statements from the incoming meta-data
* description that are not in the target description's schema.
* @see Filter::process()
* @param $input MetadataDescription
* @return MetadataDescription
*/
function &process(&$input)
{
// Create the target description
$output = new MetadataDescription($this->_toSchema);
// Compare the property names of the incoming description with
// the property names allowed in the target schema.
$sourceProperties = $input->getSetPropertyNames();
$targetProperties = $output->getPropertyNames();
$propertiesToBeRemoved = array_diff($sourceProperties, $targetProperties);
// Remove statements for properties that are not in the target schema.
$statements =& $input->getStatements();
foreach ($propertiesToBeRemoved as $propertyToBeRemoved) {
assert(isset($statements[$propertyToBeRemoved]));
unset($statements[$propertyToBeRemoved]);
}
// Set the remaining statements in the target description
$success = $output->setStatements($statements);
assert($success);
return $output;
}
