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SparqlEngine.php
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SparqlEngine.php
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<?php
require_once 'Constants.php';
require_once 'SparqlParser.php';
require_once 'SparqlQuery.php';
/**
* -----------------------------------------------------------------------------
* ERP API
* -----------------------------------------------------------------------------
*
* @author Alexander Aigner <alex.aigner (at) gmail.com>
*
* @name XPathSparqlEngine.php
* @version 2011-09-01
* @package sparql/sparqlEngine
* @access public
*
* Description The Sparql XPath Engine
*
* -----------------------------------------------------------------------------
*/
class SparqlEngine implements ISparqlEngine {
/**
* The query string
*
* @var string
*/
private $queryString;
/**
* The query object
*
* @var SparqlQuery
*/
private $query;
/**
* The model to query
*
* @var Model
*/
private $model;
/**
* List of processed variables and their resuts. Key is the subject uri or
* the variable.
*
* @var array
*/
private $processedVariables;
/**
* List of variabled that are not finnished processing. Used to prevent
* dead locks.
*
* @var array
*/
private $processingVariables;
/**
* Table of results
*
* @var array
*/
private $resultTable;
/**
* Pattern used for creating an order of queries
*
* @var array
*/
private $pattern;
/**
* Constructor
*/
function __construct() {
}
/**
* Performs a query against a model
*
* @param string $queryString
* @param Model $model
* @return mixed
*/
public static function doQuery($queryString, $model, $format = "array") {
$parser = new SparqlEngine();
return $parser->query($queryString, $model, $format);
}
/**
* Performs a query against a model
*
* @param string $queryString
* @param Model $model
* @return mixed
*/
public function query($queryString, $model, $format = "array") {
$start = $this->getTime();
if (!Check::isModel($model))
throw new SparqlException(SPARQL_ERROR . "Parameter is not a Model.");
if (!Check::isString($queryString))
throw new SparqlException(SPARQL_ERROR . "Parameter is not a string.");
$this->init();
// set first variables
$this->queryString = $queryString;
$this->model = $model;
// parse the query to an object
$parser = new SparqlParser();
$this->query = $parser->parse($queryString);
$parser = null;
switch ($this->query->getResultForm()) {
case SELECT:
$res = $this->querySelect($queryString, $model);
break;
//
// case ASK:
// throw new SparqlException(SPQRQL_QUERY_RESULT_SUPPORT);
//
// case DESCRIBE:
// throw new SparqlException(SPQRQL_QUERY_RESULT_SUPPORT);
//
// case CONSTRUCT:
// throw new SparqlException(SPQRQL_QUERY_RESULT_SUPPORT);
}
$res = $this->format($res, $format);
$end = $this->getTime();
if (Check::isArray($res)) {
$res["query"] = $this->queryString;
$res["time"] = number_format(($end - $start), 5);
}
return $res;
}
/**
* Performs a select query against a model
*
* @param string $queryString
* @param Model $model
* @return array
*/
private function querySelect($queryString, $model) {
// build the pattern for the sparql query
$pattern = $this->buildPattern();
// perform inner filters
$result = $this->applyPattern($pattern);
// filter result
$result = $this->filterBySelect($result);
return $result;
}
/**
* Formats the return value
*
* @param array $res
* @param string $format
* @return mixed
* @throws SparqlException
*/
private function format($res, $format) {
if (!Check::isArray($res))
throw new SparqlException(SPARQL_ERROR . "Array expected");
if (!Check::isString($format))
throw new SparqlException(SPARQL_ERROR . "String expected");
switch ($format) {
case "array":
return $this->formatArray($res);
case "objectarray":
return $this->formatArray($res, false);
default:
return $this->formatArray($res);
}
}
/**
* Formats result to an array
*
* @param array $res
* @param bool $stringify
* @return array
*/
private function formatArray($res, $stringify=true) {
$array = array();
foreach ($res as $key => $vars) {
$array["variables"][] = $key;
if ($stringify) {
foreach ($vars as $o) {
if (Check::isBlankNode($o))
$array["table"][$key][] = "_:" . $o->getID();
if (Check::isLiteralNode($o))
$array["table"][$key][] = $o->getLiteral();
if (Check::isResource($o) && !Check::isBlankNode($o))
$array["table"][$key][] = $o->getUri();
}
} else {
$array["table"][$key] = $vars;
}
}
return $array;
}
/**
* Resets the engine;
*/
private function init() {
$this->queryString = null;
$this->model = null;
$this->processedVariables = null;
$this->processingVariables = null;
$this->query = null;
$this->pattern = null;
}
/**
* Builds a pattern (tree) of relations of the where triple variables of the
* query.
*
* @return array
*/
private function buildPattern() {
//initiate
$this->processedVariables = null;
$this->processingVariables = null;
// retrieve tripples
$whereTriples = $this->query->getWhereTriples();
// print_r($whereTriples);
foreach ($whereTriples as $key => $triples) {
// starting with the first variable. If the variable was already
// processed it will not be checked again
if (!isset($this->processedVariables[$key]))
$this->pattern[$key] = $this->buildRecursiveTreePattern($key);
}
// freeing some memory
$this->processedVariables = null;
$this->processingVariables = null;
return $this->pattern;
}
/**
* Recursivley checks for further variables
*
* @param string $var
* @return array
*/
private function buildRecursiveTreePattern($var) {
// Variable was already processed and will be returned instead of
// processing it again.
if ($this->isVariable($var) && isset($this->processedVariables[$var]))
return $this->processedVariables[$var];
// Variable is still processed (apperently a circle in the query)
if ($this->isVariable($var) && isset($this->processingVariables[$var]))
return null;
// Get tripples and extract tripples that schould be processed
$processTriples = array();
$whereTriples = $this->query->getWhereTriples();
if (isset($whereTriples[$var]))
$processTriples = $whereTriples[$var];
// if there are no tripples found then there are no further levels to go
// and we return null;
if (empty($processTriples)) {
$this->processedVariables[$var] = $var;
return null;
}
// reset return tripples
$returnTriples = array();
// set that the variable is in process
$this->processingVariables[$var] = true;
// process the variable
foreach ($processTriples as $key => $triple) {
$object = null;
// if in the tripple the object is another variable then we will call
// this functon recursivly.
if ($this->isVariable($triple["object"])) {
// recursive call
$object = $this->buildRecursiveTreePattern($triple["object"]);
}
// if the object is set replace the original object with the set
// of triples that are returned. Otherwise we do nothing
if (!empty($object))
$triple["object"] = $object;
// we save the tripple in an array that will be returned
$returnTriples["variable"] = $var;
$returnTriples[$key] = $triple;
}
// remove the variable from the list of processing variables since no
// furhter processing is neccessary
unset($this->processingVariables[$var]);
// save the result also in the processed Variable array so if further
// calls require the same variable we dont have to process everything again
$this->processedVariables[$var] = $returnTriples;
// return the tripple with the result
return $returnTriples;
}
/**
* Applyes the pattern to the model to filter the results
*
* @param array $pattern
* @return array
*/
private function applyPattern($pattern) {
// preperation
$this->resultTable = array();
foreach ($pattern as $branch) {
$this->applyPatternRecusively($branch);
}
return $this->resultTable;
}
/**
* Helper for applyPattern($pattern)
*
* @param array $branch
* @return bool
*/
private function applyPatternRecusively($branch) {
$var = $branch["variable"];
unset($branch["variable"]);
foreach ($branch as $triple) {
// look for variables
//subject
$subject = (!$this->isVariable($triple["subject"])) ? $triple["subject"] : null;
$subjectVar = (!$this->isVariable($triple["subject"])) ? null : $triple["subject"];
//predicate
$predicate = (!$this->isVariable($triple["predicate"])) ? $triple["predicate"] : null;
$predicateVar = (!$this->isVariable($triple["predicate"])) ? null : $triple["predicate"];
//object
$object = null;
$objectVar = null;
if (is_array($triple["object"])) {
// if the object is a array it is basically a variable that has
// its own query, therefore we set it as a variable and call this
// function recursively
$objectVar = $triple["object"]["variable"];
$b = $this->applyPatternRecusively($triple["object"]);
// if the recursive call did not find any fitting objects the
// whole branch will not lead to any results. So we can cancel
// further searching
if (!$b)
return false;
} else if (!$this->isVariable($triple["object"])) {
// if the object is not a variable it has to be a node and we
// will set it
$object = $triple["object"];
} else {
// if nothing fits, the object is a variable and we set it null
$objectVar = (!$this->isVariable($triple["object"])) ? null : $triple["object"];
}
/*
* For requireing statements there need to be considered two
* possibilities:
* 1) None of the triples variables are already checked
* 2) Some of the triples variables are already checked
*
*/
// possibility (1)
if (!$this->isSetVar($subjectVar) && !$this->isSetVar($predicateVar) && !$this->isSetVar($objectVar)) {
$res = $this->model->search($subject, $predicate, $object);
// if no statements are found the whole branch will not lead to any
// results
if (empty($res))
return false;
// preparing the table;
if ($this->isVariable($subjectVar))
$this->resultTable[$subjectVar] = array();
if ($this->isVariable($predicateVar))
$this->resultTable[$predicateVar] = array();
if ($this->isVariable($objectVar))
$this->resultTable[$objectVar] = array();
// fill the table;
foreach ($res as $statement) {
if ($this->isVariable($subjectVar))
$this->resultTable[$subjectVar][] = $statement->getSubject();
if ($this->isVariable($predicateVar))
$this->resultTable[$predicateVar][] = $statement->getPredicate();
if ($this->isVariable($objectVar))
$this->resultTable[$objectVar][] = $statement->getObject();
}
} else {
//possibility 2
/*
* Here it is possible to have all combinations of the different
* variables already saved in the table:
* 1) a) ?x _o _o
* b) ?x _v _o
* c) ?x _o _v
* d) ?x _v _v
*
* 2) a) ?x ?y _o
* b) ?x ?y _v
*
* 3) a) ?x _o ?z
* b) ?x _v ?z
*
* 4) .) ?x ?y ?z
*
* 5) a) _o ?y _o
* b) _o ?y _v
* c) _v ?y _o
* d) _v ?y _v
*
* 6) a) _o ?y ?z
* b) _v ?y ?z
*
* 7 a) _o _o ?z
* b) _o _v ?z
* c) _v _o ?z
* d) _v _v ?z
*
* Description:
* ?x represent variables already in the table
* _o represent an object
* _v represents a variable that is not in the table
*
* All triples that dont contain _v are filtered and nothing is
* added, where as all triples with at least one _v can be:
* 1) removed (if no results)
* 2) variable added to the row (if one result)
* 3) row dublicated for each result (if more than one result)
*/
$deleteRows = array();
// subject possibilities 1 2 3 4
if ($this->isSetVar($subjectVar)) {
foreach ($this->resultTable[$subjectVar] as $row => $s) {
if ($this->isSetVar($predicateVar)) {
$p = $this->resultTable[$predicateVar][$row];
if ($this->isSetVar($objectVar)) {
if (!isset($this->resultTable[$objectVar][$row])) {
$res = $this->model->search($s, $p, $object);
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
}
// possibility(4)
// all variables already in the array so
// we dont have to search more
} else {
// possibility (2.a, 2.b)
$res = $this->model->search($s, $p, $object);
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
}
} else {
if ($this->isSetVar($objectVar)) {
$o = $this->resultTable[$objectVar][$row];
$res = $this->model->search($s, $predicate, $o);
// possibility (3.a, 3.b)
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
} else {
$res = $this->model->search($s, $predicate, $object);
// possibility (1.a, 1.b, 1.c, 1.d)
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
}
}
}
}
// predicate possibilities 5 & 6
if (!$this->isSetVar($subjectVar) && $this->isSetVar($predicateVar)) {
foreach ($this->resultTable[$predicateVar] as $row => $p) {
if ($this->isSetVar($objectVar)) {
$o = $this->resultTable[$objectVar][$row];
$res = $this->model->search($subject, $p, $o);
// possibility (1.a, 1.b, 1.c, 1.d)
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
} else {
$res = $this->model->search($subject, $p, $object);
// possibilities (5.a, 5.b, 5.c, 5.d)
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
}
}
}
// object possibilitie 7
if (!$this->isSetVar($subjectVar) && !$this->isSetVar($predicateVar) && $this->isSetVar($objectVar)) {
foreach ($this->resultTable[$objectVar] as $row => $o) {
$res = $this->model->search($subject, $predicate, $o);
// possibility (7.a, 7.b, 7.c, 7.d)
if (!$this->processRow($row, $res, $subjectVar, $predicateVar, $objectVar))
$deleteRows[] = $row;
}
}
// delete rows that are not part of the result
if (count($deleteRows) >= 1) {
foreach ($deleteRows as $row)
$this->removeRow($row);
}
}
}
return true;
}
/**
* Filters the result array by the select variables
*
* @param array $unfilteredResult
* @return array filtered
*/
private function filterBySelect($unfilteredResult) {
$resultVars = $this->query->getResultVariables();
foreach ($unfilteredResult as $key => $variableArray) {
if (!isset($resultVars[$key]))
unset($unfilteredResult[$key]);
}
return $unfilteredResult;
}
/**
* Checks if the parameter is a valid variable
*
* @param string $param
* @return bool
*/
private function isVariable($param) {
if (!Check::isString($param))
return false;
return (preg_match("/^\?([a-z0-9]+)$/i", $param) == 1) ? true : false;
}
/**
* Checks if a Variable is already in the result array
*
* @param string $var
* @return bool
*/
private function isSetVar($var) {
if (!$this->isVariable($var))
return false;
return isset($this->resultTable[$var]);
}
/**
* Removes a row from the result array
*
* @param int $row
*/
private function removeRow($row) {
foreach ($this->resultTable as $key => $variableArray) {
unset($variableArray[$row]);
$this->resultTable[$key] = $variableArray;
}
}
/**
* Processes a row if it was already in the result array
*
* @param integer $row row number in the array
* @param array $res results that were found and have to be considered
* @param string $sV variable name or null
* @param string $pV variable name or null
* @param string $oV variable name or null
* @return bool
*/
private function processRow($row, $res, $sV, $pV, $oV) {
// echo $row . $sV . $pV . $oV;
if (!Check::isArray($res))
return false;
if (count($res) == 0)
return false;
// check wich variables are already set
$toSetS = $this->isSetVar($sV) || $this->isVariable($sV);
$toSetP = $this->isSetVar($pV) || $this->isVariable($pV);
$toSetO = $this->isSetVar($oV) || $this->isVariable($oV);
if (count($res) == 1) {
if ($toSetS)
$this->resultTable[$sV][$row] = $res[0]->getSubject();
if ($toSetP)
$this->resultTable[$pV][$row] = $res[0]->getPredicate();
if ($toSetO)
$this->resultTable[$oV][$row] = $res[0]->getObject();
}
if (count($res) > 1) {
// if there is more than one result we might have to dublicate the row
if ($toSetS || $toSetP || $toSetO) {
// collect row data
$rowVars = array();
foreach ($this->resultTable as $key => $vars)
$rowVars[$key] = $vars[$row];
$this->removeRow($row);
foreach ($res as $statement) {
if ($toSetS)
$rowVars[$sV] = $statement->getSubject();
if ($toSetP)
$rowVars[$pV] = $statement->getPredicate();
if ($toSetO)
$rowVars[$oV] = $statement->getObject();
foreach ($rowVars as $key => $o) {
$this->resultTable[$key][] = $o;
}
}
}
}
return true;
}
/**
* Used for measuring query time
*
* @return double
*/
private function getTime() {
$a = explode(' ', microtime());
return(double) $a[0] + $a[1];
}
}
?>