RDF Parser (class_rdf

RDF Parser (class_rdf_parser.php)

Description: This class is a port to PHP of the Repat parser by Jason Diammond. Repat originally written in C was ported to PHP code using the XML parser functions of PHP, the result is a SAX-like RDF parser in native PHP code. RDF is an initiative of the W3C to describe metadata, you can find everything about RDF in the W3C site.

The class implements an event-driven interface for parsing RDF, when an RDF statement is found a handler defined by you (a PHP function) will be called and you can do whatever you want with the RDF triple (subject,predicate,object).
See usage information below and class documentation for a full description of this class.

NEWS:

06-13-2002 First version of this class released.

This class code as well as documentation are hosted at SourceForge please visit our SourceForge page for releases, documentation, bug-tracking, support forums and mailing lists.

Features

To-dos

All the valid RDF XML syntaxes defined by the W3C are supported. (See RDF XML syntax spec here)
Can parse RDF embeddded in other XML vocabulaires.
You can define SAX handlers for non-RDF XML elements. Thus allowing you to parse RDF and non-RDF in just one pass.

If you have some to-do in mind let me know it.

Contact: Luis Argerich (lrargerich@yahoo.com)

Detailed description and usage:

The first thing to do is to create an object of the class and then create a new RDF parser:

$rdf=new Rdf_parser();
$rdf->rdf_parser_create( NULL );

Now we have to define the handlers to be used, you can use the following methods to set handlers:

rdf_set_statement_handler($handler)
rdf_set_element_handler($start_handler,$end_handler);
rdf_set_warning_handler($warning_handler);
rdf_set_character_data_handler($character_data_handler);

The Statement handler

The statement handler is the most important handler since it will be the one called when RDF statements are found, we'll define the handler here and then describe each parameter:

  $rdf->rdf_set_statement_handler("my_statement_handler");
  function my_statement_handler(&$user_data, $subject_type, $subject, $predicate, 
                                 $ordinal,$object_type,$object,$xml_lang )
  {
    // Code here
  }

The statement handler parameters

Parameter	Description
user_data	user_data is a php variable that can be set using rdf_set_user_data($data),once the variable is set you can access it or use it in every handler for whatever you want.
subject_type	The subject type of the RDF statement, posible values are: RDF_SUBJECT_TYPE_URI RDF_SUBJECT_TYPE_DISTRIBUTED RDF_SUBJECT_TYPE_PREFIX RDF_SUBJECT_TYPE_ANONYMOUS
subject	The value of the subject of an RDF statement.
predicate	The predicate of an RDF statement.
ordinal	The ordinal position if the statement describes a member of a RDF collection.
object_type	The object type of the RDF statement, values are: RDF_OBJECT_TYPE_RESOURCE RDF_OBJECT_TYPE_LITERAL RDF_OBJECT_TYPE_XML
object	The value of the staement's object
xml_lang	The value of the xml_lang attribute if set

Other handlers

The start and end element handlers are triggered (if set) when some non-RDF XML element is found by the parser, the start_element_handler should receive $user_data,$name and $attributes while the end_element handler receives $user_data and $name. The character data handler

This handler is triggered when data is found outside RDF elements (if the handler is set). The handler receives two arguments: $user_data and $data containing the characters found. The warning handler

The warning handler is triggered (if set) when an RDF error is detected, teh handler receives one argument: $message containing the description of the error. Parsing

To parse a RDF document use the $rdf->rdf_parse($s,$len,$is_final) function you can parse the document by chunks calling this function many times the arguments are: $s is the data to be parsed, $len is the length of the data to be parsed and $is_final is a boolean indicating if this chunk is the last chunk of the document (no more data). The method returns true if everything went well or false if there's an XML error while parsing the document.

Method Summary
`Boolean`	`rdf_parser_create(string $encoding)` Creates an RDF parser
`void`	`rdf_parser_free(string $encoding)` Frees resources allocated by an RDF parser
`void`	`rdf_set_user_data(Any $user_data)` Sets a php variable as the parser user data
`void`	`rdf_set_statement_handler(string $handler)` Set the handler to be called when statements are found.
`void`	`rdf_set_parse_type_literal_handler(string $start, string $end)` Sets handlers for parse type literals
`void`	`rdf_set_element_handler(string $start, string $end)` Sets handlers to be called when a non-RDF element starts or ends
`void`	`rdf_set_character_data_handler(string $handler)` This allows you to define a handler for text outside RDF elements.
`void`	`rdf_set_warning_handler(string $handler)` Sets a warning handler to be called if the RDF document is broken
`Boolean`	`rdf_parse(string $s, int $len, boolean $is_final)` Parses a portion of an RDF document or a whole document
`void`	`rdf_set_base(string $base)` Sets the base name of the document being parsed

Documentation

Classes

Rdf_parser

rdf_parser_create

rdf_parser_free

rdf_set_user_data

rdf_set_statement_handler

rdf_set_parse_type_literal_handler

rdf_set_element_handler

rdf_set_character_data_handler

rdf_set_warning_handler

rdf_parse

rdf_set_base