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<?php
namespace SMW\Query\Language;
/**
* Description of a collection of many descriptions, all of which
* must be satisfied (AND, conjunction).
*
* Corresponds to conjunction in OWL and SPARQL. Not available in RDFS.
*
* @license GNU GPL v2+
* @since 1.6
*
* @author Markus Krötzsch
*/
class Conjunction extends Description {
/**
* @var Description[]
*/
protected $descriptions = [];
/**
* @since 1.6
*
* @param array $descriptions
*/
public function __construct( array $descriptions = [] ) {
foreach ( $descriptions as $description ) {
$this->addDescription( $description );
}
}
/**
* @see Description::getFingerprint
* @since 2.5
*
* @return string
*/
public function getFingerprint() {
if ( $this->fingerprint !== null ) {
return $this->fingerprint;
}
$fingerprint = [];
// Filter equal signatures
foreach ( $this->descriptions as $description ) {
$fingerprint[$description->getFingerprint()] = true;
}
// Sorting to generate a constant fingerprint independent of its
// position within a conjunction ( [Foo]][[Bar]], [[Bar]][[Foo]])
ksort( $fingerprint );
return $this->fingerprint = 'C:' . md5( implode( '|', array_keys( $fingerprint ) ) );
}
public function getDescriptions() {
return $this->descriptions;
}
public function addDescription( Description $description ) {
$this->fingerprint = null;
if ( ! ( $description instanceof ThingDescription ) ) {
if ( $description instanceof Conjunction ) { // absorb sub-conjunctions
foreach ( $description->getDescriptions() as $subdesc ) {
$this->descriptions[$subdesc->getFingerprint()] = $subdesc;
}
} else {
$this->descriptions[$description->getFingerprint()] = $description;
}
// move print descriptions downwards
///TODO: This may not be a good solution, since it does modify $description and since it does not react to future changes
$this->m_printreqs = array_merge( $this->m_printreqs, $description->getPrintRequests() );
$description->setPrintRequests( [] );
}
$fingerprint = $this->getFingerprint();
foreach ( $this->descriptions as $description ) {
$description->setMembership( $fingerprint );
}
}
public function getQueryString( $asvalue = false ) {
$result = '';
foreach ( $this->descriptions as $desc ) {
$result .= ( $result ? ' ' : '' ) . $desc->getQueryString( false );
}
if ( $result === '' ) {
return $asvalue ? '+' : '';
}
// <q> not needed for stand-alone conjunctions (AND binds stronger than OR)
return $asvalue ? " <q>{$result}</q> " : $result;
}
public function isSingleton() {
foreach ( $this->descriptions as $d ) {
if ( $d->isSingleton() ) {
return true;
}
}
return false;
}
public function getSize() {
$size = 0;
foreach ( $this->descriptions as $desc ) {
$size += $desc->getSize();
}
return $size;
}
public function getDepth() {
$depth = 0;
foreach ( $this->descriptions as $desc ) {
$depth = max( $depth, $desc->getDepth() );
}
return $depth;
}
public function getQueryFeatures() {
$result = SMW_CONJUNCTION_QUERY;
foreach ( $this->descriptions as $desc ) {
$result = $result | $desc->getQueryFeatures();
}
return $result;
}
public function prune( &$maxsize, &$maxdepth, &$log ) {
if ( $maxsize <= 0 ) {
$log[] = $this->getQueryString();
return new ThingDescription();
}
$prunelog = [];
$newdepth = $maxdepth;
$result = new Conjunction();
foreach ( $this->descriptions as $desc ) {
$restdepth = $maxdepth;
$result->addDescription( $desc->prune( $maxsize, $restdepth, $prunelog ) );
$newdepth = min( $newdepth, $restdepth );
}
if ( count( $result->getDescriptions() ) > 0 ) {
$log = array_merge( $log, $prunelog );
$maxdepth = $newdepth;
if ( count( $result->getDescriptions() ) == 1 ) { // simplify unary conjunctions!
$descriptions = $result->getDescriptions();
$result = array_shift( $descriptions );
}
$result->setPrintRequests( $this->getPrintRequests() );
return $result;
} else {
$log[] = $this->getQueryString();
$result = new ThingDescription();
$result->setPrintRequests( $this->getPrintRequests() );
return $result;
}
}
}
|
