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diff --git a/www/wiki/extensions/SemanticMediaWiki/src/Query/Language/Description.php b/www/wiki/extensions/SemanticMediaWiki/src/Query/Language/Description.php
new file mode 100644
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+++ b/www/wiki/extensions/SemanticMediaWiki/src/Query/Language/Description.php
@@ -0,0 +1,207 @@
+<?php
+
+namespace SMW\Query\Language;
+
+use SMW\Query\Exception\FingerprintNotFoundException;
+use SMW\Query\PrintRequest;
+
+/**
+ * Abstract base class for all descriptions
+ *
+ * @license GNU GPL v2+
+ * @since 1.6
+ *
+ * @author Markus Krötzsch
+ */
+abstract class Description {
+
+	/**
+	 * @var PrintRequest[]
+	 */
+	protected $m_printreqs = [];
+
+	/**
+	 * @var string|null
+	 */
+	protected $fingerprint = null;
+
+	/**
+	 * @var string
+	 */
+	private $membership = '';
+
+	/**
+	 * Get the (possibly empty) array of all print requests that
+	 * exist for the entities that fit this description.
+	 *
+	 * @return PrintRequest[]
+	 */
+	public function getPrintRequests() {
+		return $this->m_printreqs;
+	}
+
+	/**
+	 * Set the array of print requests completely.
+	 *
+	 * @param PrintRequest[] $printRequests
+	 */
+	public function setPrintRequests( array $printRequests ) {
+		$this->m_printreqs = $printRequests;
+	}
+
+	/**
+	 * Add a single SMW\Query\PrintRequest.
+	 *
+	 * @param PrintRequest $printRequest
+	 */
+	public function addPrintRequest( PrintRequest $printRequest ) {
+		$this->m_printreqs[] = $printRequest;
+	}
+
+	/**
+	 * Add a new print request, but at the beginning of the list of requests
+	 * (thus it will be printed first).
+	 *
+	 * @param PrintRequest $printRequest
+	 */
+	public function prependPrintRequest( PrintRequest $printRequest ) {
+		array_unshift( $this->m_printreqs, $printRequest );
+	}
+
+	/**
+	 * Returns a compound signature that identifies the canonized
+	 * description. It builds a fingerrint so that [[Foo::123]][[Bar::abc]]
+	 * returns the same signature as for [[Bar::abc]][[Foo::123]].
+	 *
+	 * @note An extension to a description should not rely on the query string
+	 * as sole representation for a fingerprint.
+	 *
+	 * @since 2.5
+	 *
+	 * @return string
+	 * @throws FingerprintNotFoundException
+	 */
+	public function getFingerprint() {
+
+		if ( $this->fingerprint !== null ) {
+			return $this->fingerprint;
+		}
+
+		throw new FingerprintNotFoundException( "Missing a fingerprint, a signature was expected for the current description instance." );
+	}
+
+	/**
+	 * Identifies an arbitrary membership to a wider circle of descriptions that
+	 * mostly occurs in connection with a Conjunction, Disjunction, or
+	 * SomeProperty.
+	 *
+	 * @since 2.5
+	 *
+	 * @return string
+	 */
+	public function getMembership() {
+		return $this->membership;
+	}
+
+	/**
+	 * @since 2.5
+	 *
+	 * @param string $membership
+	 */
+	public function setMembership( $membership ) {
+		$this->membership = $membership;
+	}
+
+	/**
+	 * Return a string expressing this query.
+	 * Some descriptions have different syntax in property value positions. The
+	 * parameter $asvalue specifies whether the serialisation should take that into
+	 * account.
+	 *
+	 * Example: The SMWValueDescription [[Paris]] returns the single result "Paris"
+	 * but can also be used as value in [[has location::Paris]] which is preferred
+	 * over the canonical [[has location::\<q\>[[Paris]]\</q\>]].
+	 *
+	 * The result should be a plain query string that SMW is able to parse,
+	 * without any kind of HTML escape sequences.
+	 *
+	 * @param boolean $asValue
+	 *
+	 * @return string
+	 */
+	abstract public function getQueryString( $asValue = false );
+
+	/**
+	 * Return true if the description is required to encompass at most a single
+	 * result, independently of the knowledge base.
+	 *
+	 * @return boolean
+	 */
+	abstract public function isSingleton();
+
+	/**
+	 * Compute the size of the description. Default is 1.
+	 *
+	 * @return integer
+	 */
+	public function getSize() {
+		return 1;
+	}
+
+	/**
+	 * Compute the depth of the description. Default is 0.
+	 *
+	 * @return integer
+	 */
+	public function getDepth() {
+		return 0;
+	}
+
+	/**
+	 * Report on query features used in description. Return values are (sums of)
+	 * query feature constants such as SMW_PROPERTY_QUERY.
+	 */
+	public function getQueryFeatures() {
+		return 0;
+	}
+
+	/**
+	 * Recursively restrict query to a maximal size and depth as given.
+	 * Returns a possibly changed description that should be used as a replacement.
+	 * Reduce values of parameters to account for the returned descriptions size.
+	 * Default implementation for non-nested descriptions of size 1.
+	 * The parameter $log contains a list of all pruned conditions, updated when some
+	 * description was reduced.
+	 *
+	 * @note Objects must not do changes on $this during pruning, since $this can be
+	 * reused in multiple places of one or many queries. Make new objects to reflect
+	 * changes!
+	 */
+	public function prune( &$maxsize, &$maxDepth, &$log ) {
+
+		if ( ( $maxsize < $this->getSize() ) || ( $maxDepth < $this->getDepth() ) ) {
+			$log[] = $this->getQueryString();
+
+			$result = new ThingDescription();
+			$result->setPrintRequests( $this->getPrintRequests() );
+
+			return $result;
+		}
+
+		$maxsize = $maxsize - $this->getSize();
+		$maxDepth = $maxDepth - $this->getDepth();
+
+		return $this;
+	}
+
+
+	/**
+	 * @since 3.0
+	 *
+	 * @return string
+	 */
+	public function __toString() {
+		return $this->getQueryString();
+	}
+
+}