515 lines
15 KiB
PHP
Executable File
515 lines
15 KiB
PHP
Executable File
<?php
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// ----------------------------------------------------------------------------------
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// Class: InfModelB
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// ----------------------------------------------------------------------------------
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/**
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* A InfModelB extends the InfModel Class, with a backward chaining algorithm.
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* Only the loaded or added base-triples are stored.
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* A find-query evaluates the inference rules and recursively tries to find the statements.
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* InfModelB memorises "Dead-Ends" until the next add() command, thus
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* makin a second find much faster.
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* InfModelB is safe for loops in Ontologies, that would cause infinite loops.
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* WARNING: A find(null,null,null) might take very long.
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*
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* @version $Id: InfModelB.php 290 2006-06-22 12:23:24Z tgauss $
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* @author Daniel Westphal <mail at d-westphal dot de>
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*
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* @package infModel
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* @access public
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**/
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class InfModelB extends InfModel
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{
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/**
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* Array that holds combinations of inference rules with distinct
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* find-querys, that don't lead to any inference.
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*
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* @var array
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* @access private
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*/
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var $findDeadEnds;
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/**
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* Constructor
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* You can supply a base_uri
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*
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* @param string $baseURI
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* @access public
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*/
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function InfModelB($baseURI = null)
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{
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parent::InfModel($baseURI);
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$this->findDeadEnds=array();
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}
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/**
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* Adds a new triple to the Model without checking, if the statement
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* is already in the Model. So if you want a duplicate free Model use
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* the addWithoutDuplicates() function (which is slower then add())
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*
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* @param object Statement $statement
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* @access public
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* @throws PhpError
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*/
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function add($statement)
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{
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parent::add($statement);
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//Reset the found dead-ends.
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$this->findDeadEnds=array();
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}
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/**
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* General method to search for triples.
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* NULL input for any parameter will match anything.
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* Example: $result = $m->find( NULL, NULL, $node );
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* Finds all triples with $node as object.
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* Returns an empty MemModel if nothing is found.
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* To improve the search speed with big Models, call index(INDEX_TYPE)
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* before seaching.
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*
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* It recursively searches in the statements and rules to find
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* matching statements.
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*
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* @param object Node $subject
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* @param object Node $predicate
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* @param object Node $object
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* @return object MemModel
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* @access public
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* @throws PhpError
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*/
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function find($subject,$predicate,$object)
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{
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$searchStringIndex=array();
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$resultModel=new MemModel();
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//add all infered statements without duplicates to the result model
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foreach ($this->_infFind($subject,$predicate,$object,array())as $statement)
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{
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$resultModel->addWithoutDuplicates($statement);
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};
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return $resultModel;
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}
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/**
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* This is the main inference method of the InfModelB
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* The algorithm works as follows:
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* Find all statements in the base model, that matches the current
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* find-query.
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* Check all rules, if they are able to deliver infered statements,
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* that match the current find-query. Don't use rules with queries,
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* that lead to dead-ends and don't use a rule-query-combination that
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* was used before in this branch (ontology loops).
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* If a rule is possible do deliver such statements, get a new
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* find-query, that is possible to find those statements, that are able
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* to trigger this rule.
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* Call this _infFind method wirh the new find-query and entail the
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* resulting statements.
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* If this rule, wasn't able to return any statements with this distinct
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* query, add this combination to the dead-ends.
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* Return the statements from the base triples and those, which were infered.
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*
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* If $findOnlyFirstMatching is set to true, only the first match in
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* the base-statements is entailed an returned (used in contains() and
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* findFirstMatchingStatement() methods).
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*
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* You can set an offset to look for the first matching statement by setting the
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* $offset var.
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*
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* It recursively searches in the statements and rules to find matching
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* statements
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*
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* @param object Node $subject
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* @param object Node $predicate
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* @param object Node $object
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* @param array $searchStringIndex
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* @param boolean $findOnlyFirstMatching
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* @param integer $offset
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* @param integer $resultCount
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* @return object array Statements
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* @access private
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*/
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function _infFind ($subject,$predicate,$object, $searchStringIndex, $findOnlyFirstMatching = false, $offset = 0,$resultCount = 0 )
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{
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$return=array();
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//Find all matching statements in the base statements
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$findResult=parent::find($subject,$predicate,$object);
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//For all found statements
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foreach ($findResult->triples as $statement)
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{
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$return[]=$statement;
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$resultCount++;
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//Return, if only the firstMatchingStatement was wanted
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if ($findOnlyFirstMatching && $resultCount > $offset)
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return $return;
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};
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//Don't infer statements about the schema (rdfs:subClass, etc..)
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//is false
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if ($predicate == null ||
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(is_a($predicate,'Node') &&
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!in_array($predicate->getLabel(),$this->supportedInference))
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)
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//Check only Rules, that the EntailmentIndex returned.
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foreach ($this->_findRuleEntailmentInIndex($subject,$predicate,$object) as $ruleKey)
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{
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$infRule=$this->infRules[$ruleKey];
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$serializedRuleStatement=$ruleKey.serialize($subject).serialize($predicate).serialize($object);
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//If it is to ontology loop and no dead-end
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if (!in_array($serializedRuleStatement, $searchStringIndex) &&
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!in_array($serializedRuleStatement, $this->findDeadEnds))
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{
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//Keep this distinct rule query cobination for
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//this branch to detect loops
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$searchStringIndex[]=$serializedRuleStatement;
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//If the rule is able to deliver statements that match
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//this query
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if ($infRule->checkEntailment($subject,$predicate,$object))
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{
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//Get a modified find-query, that matches statements,
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//that trigger this rule
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$modefiedFind=$infRule->getModifiedFind($subject,$predicate,$object);
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//Call this method with the new find-query
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$infFindResult=$this->_infFind($modefiedFind['s'],
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$modefiedFind['p'],
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$modefiedFind['o'],
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$searchStringIndex,
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$findOnlyFirstMatching,
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$offset,
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$resultCount) ;
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//If it deliverd statements that matches the trigger
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if (isset($infFindResult[0]))
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{
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foreach ($infFindResult as $statement)
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{
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//Entail the statements and check, if they are not about the
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//ontology
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$newStatement=$infRule->entail($statement);
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if (!in_array($newStatement->getLabelPredicate(),$this->supportedInference))
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//Check if, the entailed statements are, what we are looking for
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if($this->_nodeEqualsFind($subject,$newStatement->getSubject()) &&
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$this->_nodeEqualsFind($predicate,$newStatement->getPredicate()) &&
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$this->_nodeEqualsFind($object,$newStatement->getObject() ) )
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{
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//Add to results
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$return[]=$newStatement;
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$resultCount++;
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//or return at once
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if ($findOnlyFirstMatching && $resultCount > $offset)
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return $return;
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}
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}
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} else
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{
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//If there were no results of the rule-query-combination,
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//mark this combination as a dead-end.
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$this->findDeadEnds[]=$serializedRuleStatement;
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}
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}
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}
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}
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//Return the array of the found statements
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return $return;
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}
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/**
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* Tests if the Model contains the given triple.
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* TRUE if the triple belongs to the Model;
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* FALSE otherwise.
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*
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* @param object Statement &$statement
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* @return boolean
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* @access public
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*/
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function contains(&$statement)
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{
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//throws an error, if $statement is not of class Statement
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if(!is_a($statement,'Statement'))
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trigger_error(RDFAPI_ERROR . '(class: InfModelB; method: contains):
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$statement has to be object of class Statement', E_USER_ERROR);
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//Call the _infFind method, but let it stop, if it finds the first match.
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if (count( $this->_infFind($statement->getSubject(),
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$statement->getPredicate(),
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$statement->getObject(),
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array(),true) ) >0)
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{
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return true;
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} else
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{
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return false;
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};
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}
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/**
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* Searches for triples and returns the first matching statement.
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* NULL input for any parameter will match anything.
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* Example: $result = $m->findFirstMatchingStatement( NULL, NULL, $node );
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* Returns the first statement of the MemModel where the object equals $node.
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* Returns an NULL if nothing is found.
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* You can define an offset to search for. Default = 0
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*
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* @param object Node $subject
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* @param object Node $predicate
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* @param object Node $object
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* @param integer $offset
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* @return object Statement
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* @access public
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*/
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function findFirstMatchingStatement($subject, $predicate, $object, $offset = 0)
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{
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//Call the _infFind method, but let it stop, if it finds the
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//first match.
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$res= $this->_infFind($subject,$predicate,$object,array(),true,$offset);
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if (isset($res[$offset]))
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{
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return $res[$offset];
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} else
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{
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return NULL;
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};
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}
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/**
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* Returns a StatementIterator for traversing the Model.
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*
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* @access public
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* @return object StatementIterator
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*/
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function & getStatementIterator()
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{
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// Import Package Utility
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include_once(RDFAPI_INCLUDE_DIR.PACKAGE_UTILITY);
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// Gets a MemModel by executing a find(null,null,null) to get a
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//inferable statements.
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// WARNING: might be slow
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return new StatementIterator($this->getMemModel());
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}
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/**
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* Number of all inferable triples in the Model.
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* WARNING: uses a find(null,null,null) to find all statements! (might take a while)
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*
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* @param boolean
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* @return integer
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* @access public
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*/
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function size()
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{
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// Gets a MemModel by executing a find(null,null,null) to get a
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//inferable statements.
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// WARNING: might be slow
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$res = $this->getMemModel();
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return $res->size();
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}
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/**
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* Create a MemModel containing all the triples (including inferred
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* statements) of the current InfModelB.
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*
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* @return object MemModel
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* @access public
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*/
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function & getMemModel()
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{
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$return=$this->find(null,null,null);
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$return->setBaseURI($this->baseURI);
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$return->addParsedNamespaces($this->getParsedNamespaces());
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return $return;
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}
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/**
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* Create a MemModel containing only the base triples (without inferred
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* statements) of the current InfModelB.
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*
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* @return object MemModel
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* @access public
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*/
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function & getBaseMemModel()
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{
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$return= new MemModel();
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$return->setBaseURI($this->baseURI);
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foreach ($this->triples as $statement)
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$return->add($statement);
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$retun->addParsedNamespaces($this->getParsedNamespaces());
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return $return;
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}
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/**
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* Short Dump of the InfModelB.
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*
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* @access public
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* @return string
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*/
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function toString()
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{
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return 'InfModelB[baseURI=' . $this->getBaseURI() . '; size=' . $this->size(true) . ']';
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}
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/**
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* Dumps of the InfModelB including ALL inferable triples.
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*
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* @access public
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* @return string
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*/
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function toStringIncludingTriples()
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{
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$dump = $this->toString() . chr(13);
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$stateIt=new StatementIterator($this->find(null,null,null));
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while($statement=$stateIt->next())
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{
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$dump .= $statement->toString() . chr(13);
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}
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return $dump;
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}
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/**
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* Saves the RDF,N3 or N-Triple serialization of the full InfModelB
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* (including inferred triples) to a file.
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* You can decide to which format the model should be serialized by
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* using a corresponding suffix-string as $type parameter. If no $type
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* parameter is placed this method will serialize the model to XML/RDF
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* format.
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* Returns FALSE if the InfModelB couldn't be saved to the file.
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*
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* @access public
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* @param string $filename
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* @param string $type
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* @throws PhpError
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* @return boolean
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*/
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function saveAs($filename, $type ='rdf')
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{
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$memmodel=$this->getMemModel();
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return $memmodel->saveAs($filename, $type);
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}
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/**
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* Writes the RDF serialization of the Model including ALL inferable
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* triples as HTML.
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*
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* @access public
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*/
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function writeAsHtml()
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{
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require_once(RDFAPI_INCLUDE_DIR.PACKAGE_SYNTAX_RDF);
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$ser = new RdfSerializer();
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$rdf =& $ser->serialize($this->getMemModel());
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$rdf = htmlspecialchars($rdf, ENT_QUOTES);
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$rdf = str_replace(' ', ' ', $rdf);
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$rdf = nl2br($rdf);
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echo $rdf;
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}
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/**
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* Writes the RDF serialization of the Model including ALL inferable
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* triples as HTML table.
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*
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* @access public
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*/
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function writeAsHtmlTable()
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{
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// Import Package Utility
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include_once(RDFAPI_INCLUDE_DIR.PACKAGE_UTILITY);
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RDFUtil::writeHTMLTable($this->getMemModel());
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}
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/**
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* Writes the RDF serialization of the Model including ALL inferable
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* triples.
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*
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* @access public
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* @return string
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*/
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function writeRdfToString()
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{
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// Import Package Syntax
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include_once(RDFAPI_INCLUDE_DIR.PACKAGE_SYNTAX_RDF);
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$ser = new RdfSerializer();
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$rdf =& $ser->serialize($this->getMemModel());
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return $rdf;
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}
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/**
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* Removes the triple from the MemModel.
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* TRUE if the triple is removed.
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* FALSE otherwise.
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*
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* Checks, if it touches any statements, that added inference rules
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* to the model.
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*
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* @param object Statement $statement
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* @return boolean
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* @access public
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* @throws PhpError
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*/
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function remove($statement)
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{
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if (parent::contains($statement))
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{
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if (in_array($statement->getLabelPredicate(),$this->supportedInference));
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while (count($this->_removeFromInference($statement))>0);
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$this->findDeadEnds=array();
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return parent::remove($statement);
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} else
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{
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return false;
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}
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}
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/**
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* Checks, if a single node matches a single find pattern.
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* TRUE if the node matches.
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* FALSE otherwise.
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*
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* Checks, if it touches any statements, that added inference rules
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* to the model.
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*
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* @param object Statement $statement
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* @return boolean
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* @access private
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*/
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function _nodeEqualsFind(& $find, $node)
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{
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//If the find pattern is a node, use the nodes equal-method and
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//return the result.
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if (is_a($find,'Node'))
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return $node->equals($find);
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//Null-pattern matches anything.
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if ($find == null)
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{
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return true;
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} else
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{
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return false;
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}
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}
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/**
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* Returns a FindIterator for traversing the MemModel.
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* Disabled in InfModelB.
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*
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* @access public
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* @return object FindIterator
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*/
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function & findAsIterator($sub=null,$pred=null,$obj=null) {
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$errmsg = RDFAPI_ERROR . '(class: InfModelB; method: findAsIterator):
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This function is disabled in the
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Inference Model';
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trigger_error($errmsg, E_USER_ERROR);
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}
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}
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?>
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