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RdfWriter.php
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RdfWriter.php
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<?php
namespace Wikimedia\Purtle;
/**
* Writer interface for RDF output. RdfWriter instances are generally stateful,
* but should be implemented to operate in a stream-like manner with a minimum of state.
*
* This is intended to provide a "fluent interface" that allows programmers to use
* a turtle-like structure when generating RDF output. E.g.:
*
* @code
* $writer->prefix( 'acme', 'http://acme.test/terms/' );
* $writer->about( 'http://quux.test/Something' )
* ->say( 'acme', 'name' )->text( 'Thingy' )->text( 'Dingsda', 'de' )
* ->say( 'acme', 'owner' )->is( 'http://quux.test/' );
* @endcode
*
* To get the generated RDF output, use the drain() method.
*
* @note: The contract of this interface follows the GIGO principle, that is,
* implementations are not required to ensure valid output or prompt failure on
* invalid input. Speed should generally be favored over safety.
*
* Caveats:
* - no relative iris
* - predicates must be qnames
* - no inline/nested blank nodes
* - no comments
* - no collections
* - no automatic conversion of iris to qnames
*
* @license GPL-2.0-or-later
* @author Daniel Kinzler
*/
interface RdfWriter {
// TODO: split: generic RdfWriter class with shorthands, use RdfFormatters for output
/**
* Returns the local name of a blank node, for use with the "_" prefix.
*
* @param string|null $label node label, will be generated if not given.
*
* @return string A local name for the blank node, for use with the '_' prefix.
*/
public function blank( $label = null );
/**
* Start the document. May generate a header.
*/
public function start();
/**
* Finish the document. May generate a footer.
*
* This will detach all sub-writers that had earlier been returned by sub().
*/
public function finish();
/**
* Generates an RDF string from the current buffers state and returns it.
* The buffer is reset to the empty state.
* Before the result string is generated, implementations should close any
* pending syntactical structures (close tags, generate footers, etc).
*
* @return string The RDF output
*/
public function drain();
/**
* Declare a prefix for later use. Prefixes should be declared before being used.
* Should not be called after start().
*
* @param string $prefix
* @param string $iri a IRI
*/
public function prefix( $prefix, $iri );
/**
* Start an "about" (subject) clause, given a subject.
* Can occur at the beginning odf the output sequence, but can later only follow
* a call to is(), text(), or value().
* Should fail if called at an inappropriate time in the output sequence.
*
* @param string $base A QName prefix if $local is given, or an IRI if $local is null.
* @param string|null $local A QName suffix, or null if $base is an IRI.
*
* @return RdfWriter $this
*/
public function about( $base, $local = null );
/**
* Start a predicate clause.
* Can only follow a call to about() or say().
* Should fail if called at an inappropriate time in the output sequence.
*
* @note Unlike about() and is(), say() cannot be called with a full IRI,
* but must always use qname form. This is required to cater to output
* formats that do not allow IRIs to be used as predicates directly,
* like RDF/XML.
*
* @param string $base A QName prefix if $local is given, or a shorthand. MUST NOT be an IRI.
* @param string|null $local A QName suffix, or null if $base is a shorthand.
*
* @return RdfWriter $this
*/
public function say( $base, $local = null );
/**
* Produce a resource as the object of a statement.
* Can only follow a call to say() or a call to one of is(), text(), or value().
* Should fail if called at an inappropriate time in the output sequence.
*
* @param string $base A QName prefix if $local is given, or an IRI or shorthand if $local is null.
* @param string|null $local A QName suffix, or null if $base is an IRI or shorthand.
*
* @return RdfWriter $this
*/
public function is( $base, $local = null );
/**
* Produce a text literal as the object of a statement.
* Can only follow a call to say() or a call to one of is(), text(), or value().
* Should fail if called at an inappropriate time in the output sequence.
*
* @param string $text the text to be placed in the output
* @param string|null $language the language the text is in
*
* @return RdfWriter $this
*/
public function text( $text, $language = null );
/**
* Produce a typed or untyped literal as the object of a statement.
* Can only follow a call to say() or a call to one of is(), text(), or value().
* Should fail if called at an inappropriate time in the output sequence.
*
* @param string $value the value encoded as a string
* @param string|null $typeBase The data type's QName prefix if $typeLocal is given,
* or an IRI or shorthand if $typeLocal is null.
* @param string|null $typeLocal The data type's QName suffix,
* or null if $typeBase is an IRI or shorthand.
*
* @return RdfWriter $this
*/
public function value( $value, $typeBase = null, $typeLocal = null );
/**
* Shorthand for say( 'a' )->is( $type ).
*
* @param string $typeBase The data type's QName prefix if $typeLocal is given,
* or an IRI or shorthand if $typeLocal is null.
* @param string|null $typeLocal The data type's QName suffix,
* or null if $typeBase is an IRI or shorthand.
*
* @return RdfWriter $this
*/
public function a( $typeBase, $typeLocal = null );
/**
* Returns a document-level sub-writer.
* This can be used to generate parts statements out of sequence.
* Output generated by the sub-writer will be present in the
* return value of drain(), after any output generated by this
* writer itself.
*
* @note calling drain() on sub-writers results in undefined behavior!
* @note using sub-writers after finish() has been called on this writer
* results in undefined behavior!
*
* @return RdfWriter
*/
public function sub();
/**
* Returns the MIME type of the RDF serialization the writer produces.
*
* @return string a MIME type
*/
public function getMimeType();
}

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Aug 20 2026, 02:30 (10 w, 6 d ago)
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