File Source for InfModelB.php

<?php
// ----------------------------------------------------------------------------------
// Class: InfModelB
// ----------------------------------------------------------------------------------
/**
* A InfModelB extends the InfModel Class, with a backward chaining algorithm.
* Only the loaded or added base-triples are stored.
* A find-query evaluates the inference rules and recursively tries to find the statements.
* InfModelB memorises "Dead-Ends" until the next add() command, thus
* makin a second find much faster.
* InfModelB is safe for loops in Ontologies, that would cause infinite loops.
* WARNING: A find(null,null,null) might take very long.
*
* @version $Id: fsource_infModel__infModelInfModelB.php.html 442 2007-06-01 16:19:26Z cax $
* @author Daniel Westphal <mail at d-westphal dot de>
*
* @package infModel
* @access public
***/
class InfModelB extends InfModel
{
/**
* Array that holds combinations of inference rules with distinct
* find-querys, that don't lead to any inference.
*
* @var array
* @access private
*/
var $findDeadEnds;
/**
* Constructor
* You can supply a base_uri
*
* @param string $baseURI
* @access public
*/
function InfModelB($baseURI = null)
{
parent::InfModel($baseURI);
$this->findDeadEnds=array();
}
/**
* Adds a new triple to the Model without checking, if the statement
* is already in the Model. So if you want a duplicate free Model use
* the addWithoutDuplicates() function (which is slower then add())
*
* @param object Statement $statement
* @access public
* @throws PhpError
*/
function add($statement)
{
parent::add($statement);
//Reset the found dead-ends.
$this->findDeadEnds=array();
}
/**
* General method to search for triples.
* NULL input for any parameter will match anything.
* Example: $result = $m->find( NULL, NULL, $node );
* Finds all triples with $node as object.
* Returns an empty MemModel if nothing is found.
* To improve the search speed with big Models, call index(INDEX_TYPE)
* before seaching.
*
* It recursively searches in the statements and rules to find
* matching statements.
*
* @param object Node $subject
* @param object Node $predicate
* @param object Node $object
* @return object MemModel
* @access public
* @throws PhpError
*/
function find($subject,$predicate,$object)
{
$searchStringIndex=array();
$resultModel=new MemModel();
//add all infered statements without duplicates to the result model
foreach ($this->_infFind($subject,$predicate,$object,array())as $statement)
{
$resultModel->addWithoutDuplicates($statement);
};
return $resultModel;
}
/**
* This is the main inference method of the InfModelB
* The algorithm works as follows:
* Find all statements in the base model, that matches the current
* find-query.
* Check all rules, if they are able to deliver infered statements,
* that match the current find-query. Don't use rules with queries,
* that lead to dead-ends and don't use a rule-query-combination that
* was used before in this branch (ontology loops).
* If a rule is possible do deliver such statements, get a new
* find-query, that is possible to find those statements, that are able
* to trigger this rule.
* Call this _infFind method wirh the new find-query and entail the
* resulting statements.
* If this rule, wasn't able to return any statements with this distinct
* query, add this combination to the dead-ends.
* Return the statements from the base triples and those, which were infered.
*
* If $findOnlyFirstMatching is set to true, only the first match in
* the base-statements is entailed an returned (used in contains() and
* findFirstMatchingStatement() methods).
*
* You can set an offset to look for the first matching statement by setting the
* $offset var.
*
* It recursively searches in the statements and rules to find matching
* statements
*
* @param object Node $subject
* @param object Node $predicate
* @param object Node $object
* @param array $searchStringIndex
* @param boolean $findOnlyFirstMatching
* @param integer $offset
* @param integer $resultCount
* @return object array Statements
* @access private
*/
function _infFind ($subject,$predicate,$object, $searchStringIndex, $findOnlyFirstMatching = false, $offset = 0,$resultCount = 0 )
{
$return=array();
//Find all matching statements in the base statements
$findResult=parent::find($subject,$predicate,$object);
//For all found statements
foreach ($findResult->triples as $statement)
{
$return[]=$statement;
$resultCount++;
//Return, if only the firstMatchingStatement was wanted
if ($findOnlyFirstMatching && $resultCount > $offset)
return $return;
};
//Don't infer statements about the schema (rdfs:subClass, etc..)
//is false
if ($predicate == null ||
(is_a($predicate,'Node') &&
!in_array($predicate->getLabel(),$this->supportedInference))
)
//Check only Rules, that the EntailmentIndex returned.
foreach ($this->_findRuleEntailmentInIndex($subject,$predicate,$object) as $ruleKey)
{
$infRule=$this->infRules[$ruleKey];
$serializedRuleStatement=$ruleKey.serialize($subject).serialize($predicate).serialize($object);
//If it is to ontology loop and no dead-end
if (!in_array($serializedRuleStatement, $searchStringIndex) &&
!in_array($serializedRuleStatement, $this->findDeadEnds))
{
//Keep this distinct rule query cobination for
//this branch to detect loops
$searchStringIndex[]=$serializedRuleStatement;
//If the rule is able to deliver statements that match
//this query
if ($infRule->checkEntailment($subject,$predicate,$object))
{
//Get a modified find-query, that matches statements,
//that trigger this rule
$modefiedFind=$infRule->getModifiedFind($subject,$predicate,$object);
//Call this method with the new find-query
$infFindResult=$this->_infFind($modefiedFind['s'],
$modefiedFind['p'],
$modefiedFind['o'],
$searchStringIndex,
$findOnlyFirstMatching,
$offset,
$resultCount) ;
//If it deliverd statements that matches the trigger
if (isset($infFindResult[0]))
{
foreach ($infFindResult as $statement)
{
//Entail the statements and check, if they are not about the
//ontology
$newStatement=$infRule->entail($statement);
if (!in_array($newStatement->getLabelPredicate(),$this->supportedInference))
//Check if, the entailed statements are, what we are looking for
if($this->_nodeEqualsFind($subject,$newStatement->getSubject()) &&
$this->_nodeEqualsFind($predicate,$newStatement->getPredicate()) &&
$this->_nodeEqualsFind($object,$newStatement->getObject() ) )
{
//Add to results
$return[]=$newStatement;
$resultCount++;
//or return at once
if ($findOnlyFirstMatching && $resultCount > $offset)
return $return;
}
}
} else
{
//If there were no results of the rule-query-combination,
//mark this combination as a dead-end.
$this->findDeadEnds[]=$serializedRuleStatement;
}
}
}
}
//Return the array of the found statements
return $return;
}
/**
* Tests if the Model contains the given triple.
* TRUE if the triple belongs to the Model;
* FALSE otherwise.
*
* @param object Statement &$statement
* @return boolean
* @access public
*/
function contains(&$statement)
{
//throws an error, if $statement is not of class Statement
if(!is_a($statement,'Statement'))
trigger_error(RDFAPI_ERROR . '(class: InfModelB; method: contains):
$statement has to be object of class Statement', E_USER_ERROR);
//Call the _infFind method, but let it stop, if it finds the first match.
if (count( $this->_infFind($statement->getSubject(),
$statement->getPredicate(),
$statement->getObject(),
array(),true) ) >0)
{
return true;
} else
{
return false;
};
}
/**
* Searches for triples and returns the first matching statement.
* NULL input for any parameter will match anything.
* Example: $result = $m->findFirstMatchingStatement( NULL, NULL, $node );
* Returns the first statement of the MemModel where the object equals $node.
* Returns an NULL if nothing is found.
* You can define an offset to search for. Default = 0
*
* @param object Node $subject
* @param object Node $predicate
* @param object Node $object
* @param integer $offset
* @return object Statement
* @access public
*/
function findFirstMatchingStatement($subject, $predicate, $object, $offset = 0)
{
//Call the _infFind method, but let it stop, if it finds the
//first match.
$res= $this->_infFind($subject,$predicate,$object,array(),true,$offset);
if (isset($res[$offset]))
{
return $res[$offset];
} else
{
return NULL;
};
}
/**
* Returns a StatementIterator for traversing the Model.
*
* @access public
* @return object StatementIterator
*/
function & getStatementIterator()
{
// Import Package Utility
include_once(RDFAPI_INCLUDE_DIR.PACKAGE_UTILITY);
// Gets a MemModel by executing a find(null,null,null) to get a
//inferable statements.
// WARNING: might be slow
return new StatementIterator($this->getMemModel());
}
/**
* Number of all inferable triples in the Model.
* WARNING: uses a find(null,null,null) to find all statements! (might take a while)
*
* @param boolean
* @return integer
* @access public
*/
function size()
{
// Gets a MemModel by executing a find(null,null,null) to get a
//inferable statements.
// WARNING: might be slow
$res = $this->getMemModel();
return $res->size();
}
/**
* Create a MemModel containing all the triples (including inferred
* statements) of the current InfModelB.
*
* @return object MemModel
* @access public
*/
function & getMemModel()
{
$return=$this->find(null,null,null);
$return->setBaseURI($this->baseURI);
$return->addParsedNamespaces($this->getParsedNamespaces());
return $return;
}
/**
* Create a MemModel containing only the base triples (without inferred
* statements) of the current InfModelB.
*
* @return object MemModel
* @access public
*/
function & getBaseMemModel()
{
$return= new MemModel();
$return->setBaseURI($this->baseURI);
foreach ($this->triples as $statement)
$return->add($statement);
$retun->addParsedNamespaces($this->getParsedNamespaces());
return $return;
}
/**
* Short Dump of the InfModelB.
*
* @access public
* @return string
*/
function toString()
{
return 'InfModelB[baseURI=' . $this->getBaseURI() . '; size=' . $this->size(true) . ']';
}
/**
* Dumps of the InfModelB including ALL inferable triples.
*
* @access public
* @return string
*/
function toStringIncludingTriples()
{
$dump = $this->toString() . chr(13);
$stateIt=new StatementIterator($this->find(null,null,null));
while($statement=$stateIt->next())
{
$dump .= $statement->toString() . chr(13);
}
return $dump;
}
/**
* Saves the RDF,N3 or N-Triple serialization of the full InfModelB
* (including inferred triples) to a file.
* You can decide to which format the model should be serialized by
* using a corresponding suffix-string as $type parameter. If no $type
* parameter is placed this method will serialize the model to XML/RDF
* format.
* Returns FALSE if the InfModelB couldn't be saved to the file.
*
* @access public
* @param string $filename
* @param string $type
* @throws PhpError
* @return boolean
*/
function saveAs($filename, $type ='rdf')
{
$memmodel=$this->getMemModel();
return $memmodel->saveAs($filename, $type);
}
/**
* Writes the RDF serialization of the Model including ALL inferable
* triples as HTML.
*
* @access public
*/
function writeAsHtml()
{
require_once(RDFAPI_INCLUDE_DIR.PACKAGE_SYNTAX_RDF);
$ser = new RdfSerializer();
$rdf =& $ser->serialize($this->getMemModel());
$rdf = htmlspecialchars($rdf, ENT_QUOTES);
$rdf = str_replace(' ', ' ', $rdf);
$rdf = nl2br($rdf);
echo $rdf;
}
/**
* Writes the RDF serialization of the Model including ALL inferable
* triples as HTML table.
*
* @access public
*/
function writeAsHtmlTable()
{
// Import Package Utility
include_once(RDFAPI_INCLUDE_DIR.PACKAGE_UTILITY);
RDFUtil::writeHTMLTable($this->getMemModel());
}
/**
* Writes the RDF serialization of the Model including ALL inferable
* triples.
*
* @access public
* @return string
*/
function writeRdfToString()
{
// Import Package Syntax
include_once(RDFAPI_INCLUDE_DIR.PACKAGE_SYNTAX_RDF);
$ser = new RdfSerializer();
$rdf =& $ser->serialize($this->getMemModel());
return $rdf;
}
/**
* Removes the triple from the MemModel.
* TRUE if the triple is removed.
* FALSE otherwise.
*
* Checks, if it touches any statements, that added inference rules
* to the model.
*
* @param object Statement $statement
* @return boolean
* @access public
* @throws PhpError
*/
function remove($statement)
{
if (parent::contains($statement))
{
if (in_array($statement->getLabelPredicate(),$this->supportedInference));
while (count($this->_removeFromInference($statement))>0);
$this->findDeadEnds=array();
return parent::remove($statement);
} else
{
return false;
}
}
/**
* Checks, if a single node matches a single find pattern.
* TRUE if the node matches.
* FALSE otherwise.
*
* Checks, if it touches any statements, that added inference rules
* to the model.
*
* @param object Statement $statement
* @return boolean
* @access private
*/
function _nodeEqualsFind(& $find, $node)
{
//If the find pattern is a node, use the nodes equal-method and
//return the result.
if (is_a($find,'Node'))
return $node->equals($find);
//Null-pattern matches anything.
if ($find == null)
{
return true;
} else
{
return false;
}
}
/**
* Returns a FindIterator for traversing the MemModel.
* Disabled in InfModelB.
*
* @access public
* @return object FindIterator
*/
function & findAsIterator($sub=null,$pred=null,$obj=null) {
$errmsg = RDFAPI_ERROR . '(class: InfModelB; method: findAsIterator):
This function is disabled in the
Inference Model';
trigger_error($errmsg, E_USER_ERROR);
}
}
?>

Documentation generated on Fri, 1 Jun 2007 16:49:27 +0200 by phpDocumentor 1.3.2

Source for file InfModelB.php