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<?php
use SMW\InMemoryPoolCache;
/**
* File holding the SMWTurtleSerializer class that provides basic functions for
* serialising OWL data in Turtle syntax.
*
* @ingroup SMW
*
* @author Markus Krötzsch
*/
/**
* Class for serializing exported data (encoded as SMWExpData object) in
* Turtle syntax.
*
* @ingroup SMW
*/
class SMWTurtleSerializer extends SMWSerializer {
/**
* Array of non-trivial sub-SMWExpData elements that cannot be nested while
* serializing some SMWExpData. The elements of the array are serialized
* later during the same serialization step (so this is not like another
* queue for declarations or the like; it just unfolds an SMWExpData
* object).
*
* @var array of SMWExpData
*/
protected $subexpdata;
/**
* If true, do not serialize namespace declarations and record them in
* $sparql_namespaces instead for later retrieval.
* @var boolean
*/
protected $sparqlmode;
/**
* Array of retrieved namespaces (abbreviation => URI) for later use.
* @var array of string
*/
protected $sparql_namespaces;
public function __construct( $sparqlMode = false ) {
parent::__construct();
$this->sparqlmode = $sparqlMode;
}
public function clear() {
parent::clear();
$this->sparql_namespaces = [];
}
/**
* @since 2.3
*/
public static function reset() {
InMemoryPoolCache::getInstance()->resetPoolCacheById( 'turtle.serializer' );
}
/**
* Get an array of namespace prefixes used in SPARQL mode.
* Namespaces are not serialized among triples in SPARQL mode but are
* collected separately. This method returns the prefixes and empties
* the collected list afterwards.
*
* @return array shortName => namespace URI
*/
public function flushSparqlPrefixes() {
$result = $this->sparql_namespaces;
$this->sparql_namespaces = [];
return $result;
}
protected function serializeHeader() {
if ( $this->sparqlmode ) {
$this->pre_ns_buffer = '';
$this->sparql_namespaces = [
"rdf" => SMWExporter::getInstance()->expandURI( '&rdf;' ),
"rdfs" => SMWExporter::getInstance()->expandURI( '&rdfs;' ),
"owl" => SMWExporter::getInstance()->expandURI( '&owl;' ),
"swivt" => SMWExporter::getInstance()->expandURI( '&swivt;' ),
"wiki" => SMWExporter::getInstance()->expandURI( '&wiki;' ),
"category" => SMWExporter::getInstance()->expandURI( '&category;' ),
"property" => SMWExporter::getInstance()->expandURI( '&property;' ),
"xsd" => "http://www.w3.org/2001/XMLSchema#" ,
"wikiurl" => SMWExporter::getInstance()->expandURI( '&wikiurl;' )
];
} else {
$this->pre_ns_buffer =
"@prefix rdf: <" . SMWExporter::getInstance()->expandURI( '&rdf;' ) . "> .\n" .
"@prefix rdfs: <" . SMWExporter::getInstance()->expandURI( '&rdfs;' ) . "> .\n" .
"@prefix owl: <" . SMWExporter::getInstance()->expandURI( '&owl;' ) . "> .\n" .
"@prefix swivt: <" . SMWExporter::getInstance()->expandURI( '&swivt;' ) . "> .\n" .
// A note on "wiki": this namespace is crucial as a fallback when it would be illegal to start e.g. with a number.
// In this case, one can always use wiki:... followed by "_" and possibly some namespace, since _ is legal as a first character.
"@prefix wiki: <" . SMWExporter::getInstance()->expandURI( '&wiki;' ) . "> .\n" .
"@prefix category: <" . SMWExporter::getInstance()->expandURI( '&category;' ) . "> .\n" .
"@prefix property: <" . SMWExporter::getInstance()->expandURI( '&property;' ) . "> .\n" .
"@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .\n" . // note that this XSD URI is hardcoded below (its unlikely to change, of course)
"@prefix wikiurl: <" . SMWExporter::getInstance()->expandURI( '&wikiurl;' ) . "> .\n";
}
$this->global_namespaces = [ 'rdf' => true, 'rdfs' => true, 'owl' => true, 'swivt' => true, 'wiki' => true, 'property' => true, 'category' => true ];
$this->post_ns_buffer = "\n";
}
protected function serializeFooter() {
if ( !$this->sparqlmode ) {
$this->post_ns_buffer .= "\n# Created by Semantic MediaWiki, https://www.semantic-mediawiki.org/\n";
}
}
public function serializeDeclaration( $uri, $typename ) {
$this->post_ns_buffer .= "<" . SMWExporter::getInstance()->expandURI( $uri ) . "> rdf:type $typename .\n";
}
public function serializeExpData( SMWExpData $expData ) {
$this->subExpData = [ $expData ];
while ( count( $this->subExpData ) > 0 ) {
$this->serializeNestedExpData( array_pop( $this->subExpData ), '' );
}
$this->serializeNamespaces();
}
protected function serializeNamespace( $shortname, $uri ) {
$this->global_namespaces[$shortname] = true;
if ( $this->sparqlmode ) {
$this->sparql_namespaces[$shortname] = $uri;
} else {
$this->pre_ns_buffer .= "@prefix $shortname: <$uri> .\n";
}
}
/**
* Serialize the given SMWExpData object, possibly recursively with
* increased indentation.
*
* @param $data SMWExpData containing the data to be serialised.
* @param $indent string specifying a prefix for indentation (usually a sequence of tabs)
*/
protected function serializeNestedExpData( SMWExpData $data, $indent ) {
if ( count( $data->getProperties() ) == 0 ) {
return; // nothing to export
}
// Avoid posting turtle property declarations already known for the
// subject more than once
if ( $data->getSubject()->getDataItem() !== null && $data->getSubject()->getDataItem()->getNamespace() === SMW_NS_PROPERTY ) {
$hash = $data->getHash();
$poolCache = InMemoryPoolCache::getInstance()->getPoolCacheById( 'turtle.serializer' );
if ( $poolCache->contains( $hash ) && $poolCache->fetch( $hash ) ) {
return;
}
$poolCache->save( $hash, true );
}
$this->recordDeclarationTypes( $data );
$bnode = false;
$this->post_ns_buffer .= $indent;
if ( !$data->getSubject()->isBlankNode() ) {
$this->serializeExpResource( $data->getSubject() );
} else { // blank node
$bnode = true;
$this->post_ns_buffer .= "[";
}
if ( ( $indent !== '' ) && ( !$bnode ) ) { // called to generate a nested descripion; but Turtle cannot nest non-bnode descriptions, do this later
$this->subexpdata[] = $data;
return;
} elseif ( !$bnode ) {
$this->post_ns_buffer .= "\n ";
}
$firstproperty = true;
foreach ( $data->getProperties() as $property ) {
$this->post_ns_buffer .= $firstproperty ? "\t" : " ;\n $indent\t";
$firstproperty = false;
$prop_decl_queued = false;
$class_type_prop = $this->isOWLClassTypeProperty( $property );
$this->serializeExpResource( $property );
$firstvalue = true;
foreach ( $data->getValues( $property ) as $value ) {
$this->post_ns_buffer .= $firstvalue ? ' ' : ' , ';
$firstvalue = false;
if ( $value instanceof SMWExpLiteral ) {
$prop_decl_type = SMW_SERIALIZER_DECL_APROP;
$this->serializeExpLiteral( $value );
} elseif ( $value instanceof SMWExpResource ) {
$prop_decl_type = SMW_SERIALIZER_DECL_OPROP;
$this->serializeExpResource( $value );
} elseif ( $value instanceof SMWExpData ) { // resource (maybe blank node), could have subdescriptions
$prop_decl_type = SMW_SERIALIZER_DECL_OPROP;
$collection = $value->getCollection();
if ( $collection !== false ) { // RDF-style collection (list)
$this->post_ns_buffer .= "( ";
foreach ( $collection as $subvalue ) {
$this->serializeNestedExpData( $subvalue, $indent . "\t\t" );
if ( $class_type_prop ) {
$this->requireDeclaration( $subvalue->getSubject(), SMW_SERIALIZER_DECL_CLASS );
}
}
$this->post_ns_buffer .= " )";
} else {
if ( $class_type_prop ) {
$this->requireDeclaration( $value->getSubject(), SMW_SERIALIZER_DECL_CLASS );
}
if ( count( $value->getProperties() ) > 0 ) { // resource with data: serialise
$this->post_ns_buffer .= "\n";
$this->serializeNestedExpData( $value, $indent . "\t\t" );
} else { // resource without data: may need to be queued
$this->serializeExpResource( $value->getSubject() );
}
}
}
if ( !$prop_decl_queued ) {
$this->requireDeclaration( $property, $prop_decl_type );
$prop_decl_queued = true;
}
}
}
$this->post_ns_buffer .= ( $bnode ? " ]" : " ." ) . ( $indent === '' ? "\n\n" : '' );
}
protected function serializeExpLiteral( SMWExpLiteral $element ) {
$this->post_ns_buffer .= self::getTurtleNameForExpElement( $element );
}
protected function serializeExpResource( SMWExpResource $element ) {
if ( $element instanceof SMWExpNsResource ) {
$this->requireNamespace( $element->getNamespaceID(), $element->getNamespace() );
}
$this->post_ns_buffer .= self::getTurtleNameForExpElement( $element );
}
/**
* Get the Turtle serialization string for the given SMWExpElement. The
* method just computes a name, and does not serialize triples, so the
* parameter must be an SMWExpResource or SMWExpLiteral, no SMWExpData.
*
* @param $expElement SMWExpElement being SMWExpLiteral or SMWExpResource
* @return string
*/
public static function getTurtleNameForExpElement( SMWExpElement $expElement ) {
if ( $expElement instanceof SMWExpResource ) {
if ( $expElement->isBlankNode() ) {
return '[]';
} elseif ( ( $expElement instanceof SMWExpNsResource ) && ( $expElement->hasAllowedLocalName() ) ) {
return $expElement->getQName();
} else {
return '<' . str_replace( '>', '\>', SMWExporter::getInstance()->expandURI( $expElement->getUri() ) ) . '>';
}
} elseif ( $expElement instanceof SMWExpLiteral ) {
$dataType = $expElement->getDatatype();
$lexicalForm = self::getCorrectLexicalForm( $expElement );
if ( ( $dataType !== '' ) && ( $dataType != 'http://www.w3.org/2001/XMLSchema#string' ) ) {
$count = 0;
$newdt = str_replace( 'http://www.w3.org/2001/XMLSchema#', 'xsd:', $dataType, $count );
return ( $count == 1 ) ? "$lexicalForm^^$newdt" : "$lexicalForm^^<$dataType>";
} else {
return $lexicalForm;
}
} else {
throw new InvalidArgumentException( 'The method can only serialize atomic elements of type SMWExpResource or SMWExpLiteral.' );
}
}
private static function getCorrectLexicalForm( $expElement ) {
$lexicalForm = str_replace( [ '\\', "\n", '"' ], [ '\\\\', "\\n", '\"' ], $expElement->getLexicalForm() );
if ( $expElement->getLang() !== '' && ( $expElement->getDatatype() === 'http://www.w3.org/1999/02/22-rdf-syntax-ns#langString' ) ) {
$lexicalForm = '"' . $lexicalForm . '@' . $expElement->getLang() . '"';
} elseif ( $expElement->getLang() !== '' ) {
$lexicalForm = '"' . $lexicalForm . '"'. '@' . $expElement->getLang();
} else {
$lexicalForm = '"' . $lexicalForm . '"';
}
return $lexicalForm;
}
}
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