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<?php
namespace SMW\SPARQLStore\QueryEngine\Condition;
/**
* Abstract class that represents a SPARQL (sub-)pattern and relevant pieces
* of associated information for using it in query building.
*
* @ingroup SMWStore
*
* @license GNU GPL v2+
* @since 1.6
*
* @author Markus Krötzsch
*/
abstract class Condition {
/**
* If results could be ordered by the things that this condition
* matches, then this is the name of the variable to use in ORDER BY.
* Otherwise it is ''.
* @note SPARQL variable names do not include the initial "?" or "$".
* @var string
*/
public $orderByVariable = '';
/**
* Array that relates sortkeys (given by the users, i.e. property
* names) to variable names in the generated SPARQL query.
* Format sortkey => variable name
* @var array
*/
public $orderVariables = [];
/**
* Associative array of additional conditions that should not narrow
* down the set of results, but that introduce some relevant variable,
* typically for ordering. For instance, selecting the sortkey of a
* page needs only be done once per query. The array is indexed by the
* name of the (main) selected variable, e.g. "v42sortkey" to allow
* elimination of duplicate weak conditions that aim to introduce this
* variable.
* @var array of format "condition identifier" => "condition"
*/
public $weakConditions = [];
/**
* Associative array of additional conditions that should can narrow
* down the set of results,
*
* @var array of format "condition identifier" => "condition"
*/
public $cogentConditions = [];
/**
* Associative array of additional namespaces that this condition
* requires to be declared
* @var array of format "shortName" => "namespace URI"
*/
public $namespaces = [];
/**
* Get the SPARQL condition string that this object represents. This
* does not include the weak conditions, or additional formulations to
* match singletons (see SMWSparqlSingletonCondition).
*
* @return string
*/
abstract public function getCondition();
/**
* Tell whether the condition string returned by getCondition() is safe
* in the sense that it can be used alone in a SPARQL query. This
* requires that all filtered variables occur in some graph pattern,
* and that the condition is not empty.
*
* @return boolean
*/
abstract public function isSafe();
public function addNamespaces( array $namespaces ) {
$this->namespaces = array_merge( $this->namespaces, $namespaces );
}
public function getWeakConditionString() {
return implode( '', $this->weakConditions );
}
public function getCogentConditionString() {
return implode( '', $this->cogentConditions );
}
}
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