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<?php
/**
* File holding the SMWRDFXMLSerializer class that provides basic functions for
* serialising OWL data in RDF/XML syntax.
*
* @ingroup SMW
*
* @author Markus Krötzsch
*/
/**
* Class for serializing exported data (encoded as SMWExpData object) in
* RDF/XML.
*
* @ingroup SMW
*/
class SMWRDFXMLSerializer extends SMWSerializer {
/**
* True if the $pre_ns_buffer contains the beginning of a namespace
* declaration block to which further declarations for the current
* context can be appended.
*/
protected $namespace_block_started;
/**
* True if the namespaces that are added at the current serialization stage
* become global, i.e. remain available for all later contexts. This is the
* case in RDF/XML only as long as the header has not been streamed to the
* client (reflected herein by calling flushContent()). Later, namespaces
* can only be added locally to individual elements, thus requiring them to
* be re-added multiple times if used in many elements.
*/
protected $namespaces_are_global;
public function clear() {
parent::clear();
$this->namespaces_are_global = false;
$this->namespace_block_started = false;
}
protected function serializeHeader() {
$this->namespaces_are_global = true;
$this->namespace_block_started = true;
$this->pre_ns_buffer =
"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" .
"<!DOCTYPE rdf:RDF[\n" .
"\t<!ENTITY rdf " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&rdf;' ) ) . ">\n" .
"\t<!ENTITY rdfs " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&rdfs;' ) ) . ">\n" .
"\t<!ENTITY owl " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&owl;' ) ) . ">\n" .
"\t<!ENTITY swivt " . $this->makeValueEntityString( 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.
"\t<!ENTITY wiki " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&wiki;' ) ) . ">\n" .
"\t<!ENTITY category " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&category;' ) ) . ">\n" .
"\t<!ENTITY property " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&property;' ) ) . ">\n" .
"\t<!ENTITY wikiurl " . $this->makeValueEntityString( SMWExporter::getInstance()->expandURI( '&wikiurl;' ) ) . ">\n" .
"]>\n\n" .
"<rdf:RDF\n" .
"\txmlns:rdf=\"&rdf;\"\n" .
"\txmlns:rdfs=\"&rdfs;\"\n" .
"\txmlns:owl =\"&owl;\"\n" .
"\txmlns:swivt=\"&swivt;\"\n" .
"\txmlns:wiki=\"&wiki;\"\n" .
"\txmlns:category=\"&category;\"\n" .
"\txmlns:property=\"&property;\"";
$this->global_namespaces = [ 'rdf' => true, 'rdfs' => true, 'owl' => true, 'swivt' => true, 'wiki' => true, 'property' => true, 'category' => true ];
$this->post_ns_buffer .= ">\n\n";
}
protected function serializeFooter() {
$this->post_ns_buffer .= "\t<!-- Created by Semantic MediaWiki, https://www.semantic-mediawiki.org/ -->\n";
$this->post_ns_buffer .= '</rdf:RDF>';
}
public function serializeDeclaration( $uri, $typename ) {
$this->post_ns_buffer .= "\t<$typename rdf:about=\"$uri\" />\n";
}
public function serializeExpData( SMWExpData $expData ) {
$this->serializeNestedExpData( $expData, '' );
$this->serializeNamespaces();
if ( !$this->namespaces_are_global ) {
$this->pre_ns_buffer .= $this->post_ns_buffer;
$this->post_ns_buffer = '';
$this->namespace_block_started = false;
}
}
public function flushContent() {
$result = parent::flushContent();
$this->namespaces_are_global = false; // must not be done before calling the parent method (which may declare namespaces)
$this->namespace_block_started = false;
return $result;
}
protected function serializeNamespace( $shortname, $uri ) {
if ( $this->namespaces_are_global ) {
$this->global_namespaces[$shortname] = true;
$this->pre_ns_buffer .= "\n\t";
} else {
$this->pre_ns_buffer .= ' ';
}
$this->pre_ns_buffer .= "xmlns:$shortname=\"$uri\"";
}
/**
* Serialize the given SMWExpData object, possibly recursively with
* increased indentation.
*
* @param $expData SMWExpData containing the data to be serialised.
* @param $indent string specifying a prefix for indentation (usually a sequence of tabs)
*/
protected function serializeNestedExpData( SMWExpData $expData, $indent ) {
$this->recordDeclarationTypes( $expData );
$type = $expData->extractMainType()->getQName();
if ( !$this->namespace_block_started ) { // start new ns block
$this->pre_ns_buffer .= "\t$indent<$type";
$this->namespace_block_started = true;
} else { // continue running block
$this->post_ns_buffer .= "\t$indent<$type";
}
if ( ( $expData->getSubject() instanceof SMWExpResource ) &&
!$expData->getSubject()->isBlankNode() ) {
$this->post_ns_buffer .= ' rdf:about="' . $expData->getSubject()->getUri() . '"';
} // else: blank node, no "rdf:about"
if ( count( $expData->getProperties() ) == 0 ) { // nothing else to export
$this->post_ns_buffer .= " />\n";
} else { // process data
$this->post_ns_buffer .= ">\n";
foreach ( $expData->getProperties() as $property ) {
$prop_decl_queued = false;
$isClassTypeProp = $this->isOWLClassTypeProperty( $property );
foreach ( $expData->getValues( $property ) as $valueElement ) {
$this->requireNamespace( $property->getNamespaceID(), $property->getNamespace() );
if ( $valueElement instanceof SMWExpLiteral ) {
$prop_decl_type = SMW_SERIALIZER_DECL_APROP;
$this->serializeExpLiteral( $property, $valueElement, "\t\t$indent" );
} elseif ( $valueElement instanceof SMWExpResource ) {
$prop_decl_type = SMW_SERIALIZER_DECL_OPROP;
$this->serializeExpResource( $property, $valueElement, "\t\t$indent", $isClassTypeProp );
} elseif ( $valueElement instanceof SMWExpData ) {
$prop_decl_type = SMW_SERIALIZER_DECL_OPROP;
$collection = $valueElement->getCollection();
if ( $collection !== false ) { // RDF-style collection (list)
$this->serializeExpCollection( $property, $collection, "\t\t$indent", $isClassTypeProp );
} elseif ( count( $valueElement->getProperties() ) > 0 ) { // resource with data
$this->post_ns_buffer .= "\t\t$indent<" . $property->getQName() . ">\n";
$this->serializeNestedExpData( $valueElement, "\t\t$indent" );
$this->post_ns_buffer .= "\t\t$indent</" . $property->getQName() . ">\n";
} else { // resource without data
$this->serializeExpResource( $property, $valueElement->getSubject(), "\t\t$indent", $isClassTypeProp );
}
} // else: no other types of export elements
if ( !$prop_decl_queued ) {
$this->requireDeclaration( $property, $prop_decl_type );
$prop_decl_queued = true;
}
}
}
$this->post_ns_buffer .= "\t$indent</" . $type . ">\n";
}
}
/**
* Add to the output a serialization of a property assignment where an
* SMWExpLiteral is the object. It is assumed that a suitable subject
* block has already been openend.
*
* @param $expResourceProperty SMWExpNsResource the property to use
* @param $expLiteral SMWExpLiteral the data value to use
* @param $indent string specifying a prefix for indentation (usually a sequence of tabs)
*/
protected function serializeExpLiteral( SMWExpNsResource $expResourceProperty, SMWExpLiteral $expLiteral, $indent ) {
$this->post_ns_buffer .= $indent . '<' . $expResourceProperty->getQName();
// https://www.w3.org/TR/rdf-syntax-grammar/#section-Syntax-languages
// "... to indicate that the included content is in the given language.
// Typed literals which includes XML literals are not affected by this
// attribute. The most specific in-scope language present (if any) is
// applied to property element string literal ..."
if ( $expLiteral->getDatatype() !== '' && $expLiteral->getLang() !== '' ) {
$this->post_ns_buffer .= ' xml:lang="' . $expLiteral->getLang() . '"';
} elseif ( $expLiteral->getDatatype() !== '' ) {
$this->post_ns_buffer .= ' rdf:datatype="' . $expLiteral->getDatatype() . '"';
}
$this->post_ns_buffer .= '>' . $this->makeAttributeValueString( $expLiteral->getLexicalForm() );
$this->post_ns_buffer .= '</' . $expResourceProperty->getQName() . ">\n";
}
/**
* Add to the output a serialization of a property assignment where an
* SMWExpResource is the object. It is assumed that a suitable subject
* block has already been openend.
*
* @param $expResourceProperty SMWExpNsResource the property to use
* @param $expResource SMWExpResource the data value to use
* @param $indent string specifying a prefix for indentation (usually a sequence of tabs)
* @param $isClassTypeProp boolean whether the resource must be declared as a class
*/
protected function serializeExpResource( SMWExpNsResource $expResourceProperty, SMWExpResource $expResource, $indent, $isClassTypeProp ) {
$this->post_ns_buffer .= $indent . '<' . $expResourceProperty->getQName();
if ( !$expResource->isBlankNode() ) {
if ( ( $expResource instanceof SMWExpNsResource ) && ( $expResource->getNamespaceID() == 'wiki' ) ) {
// very common case, reduce bandwidth
$this->post_ns_buffer .= ' rdf:resource="&wiki;' . $expResource->getLocalName() . '"';
} else {
$uriValue = $this->makeAttributeValueString( $expResource->getUri() );
$this->post_ns_buffer .= ' rdf:resource="' . $uriValue . '"';
}
}
$this->post_ns_buffer .= "/>\n";
if ( $isClassTypeProp ) {
$this->requireDeclaration( $expResource, SMW_SERIALIZER_DECL_CLASS );
}
}
/**
* Add a serialization of the given SMWExpResource to the output,
* assuming that an opening property tag is alerady there.
*
* @param $expResourceProperty SMWExpNsResource the property to use
* @param $expResource array of (SMWExpResource or SMWExpData)
* @param $indent string specifying a prefix for indentation (usually a sequence of tabs)
* @param $isClassTypeProp boolean whether the resource must be declared as a class
*
* @bug The $isClassTypeProp parameter is not properly taken into account.
* @bug Individual resources are not serialised properly.
*/
protected function serializeExpCollection( SMWExpNsResource $expResourceProperty, array $collection, $indent, $isClassTypeProp ) {
$this->post_ns_buffer .= $indent . '<' . $expResourceProperty->getQName() . " rdf:parseType=\"Collection\">\n";
foreach ( $collection as $expElement ) {
if ( $expElement instanceof SMWExpData ) {
$this->serializeNestedExpData( $expElement, $indent );
} else {
// FIXME: the below is not the right thing to do here
//$this->serializeExpResource( $expResourceProperty, $expElement, $indent );
}
if ( $isClassTypeProp ) {
// FIXME: $expResource is undefined
//$this->requireDeclaration( $expResource, SMW_SERIALIZER_DECL_CLASS );
}
}
$this->post_ns_buffer .= "$indent</" . $expResourceProperty->getQName() . ">\n";
}
/**
* Escape a string in the special form that is required for values in
* DTD entity declarations in XML. Namely, this require the percent sign
* to be replaced.
*
* @param $string string to be escaped
* @return string
*/
protected function makeValueEntityString( $string ) {
return "'" . str_replace( '%', '%', $string ) . "'";
}
/**
* Escape a string as required for using it in XML attribute values.
*
* @param $string string to be escaped
* @return string
*/
protected function makeAttributeValueString( $string ) {
return str_replace( [ '&', '>', '<' ], [ '&', '>', '<' ], $string );
}
}
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