librdf/rdf_parser.php

<?php
// ##################################################################################
// Title                     : Class Rdf_parser
// Version                   : 1.5.0
// Author                    : Jason Diammond -repat RDF parser-
//                           : Luis Argerich -PHP version of repat- (lrargerich@yahoo.com)
//                           : Matt A. Tobin -Continued PHP Compat- (email@mattatobin.com)
// Last modification date    : See history below..
// Description               : A port to PHP of the Repat an RDF parser.
//                             This parser based on expat parses RDF files producing events
//                             proper of RDF documents.
// ##################################################################################
// History:
// 06-13-2002                : First version of this class.
// 07-17-2002                : Minor bugfix (Leandro Mariano Lopez)
// 08-16-2006                : Allowed for user callback function to be in a class
//                             (Justin Scott)
// 10-05-2017                : Fixed issues with PHP 7 namely the ereg() polyfill
// 12-21-2018                : Fix rdf parser lib for outdated usage of call_user_func
// 02-26-2020                : PHP 7.4 Compat
// ??-??-2021                : PHP 8.x Compat
// 02-17-2022                : Use constants for common chars
// ##################################################################################
// To-Dos:
//   Keep it working..
// ##################################################################################
// How to use it:
// Read the documentation in rdf_parser.html
// ##################################################################################

class Rdf_parser {
  const EMPTY_STRING                    = '';
  const DOT                             = '.';
  const DASH                            = '-';
  const UNDERSCORE                      = '_';
  const COLON                           = ':';

  const XML_NAMESPACE_URI               = 'http://www.w3.org/XML/1998/namespace';
  const XML_LANG                        = 'lang';
  const RDF_NAMESPACE_URI               = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#';
  const RDF_RDF                         = 'RDF';
  const RDF_DESCRIPTION                 = 'Description';
  const RDF_ID                          = 'ID';
  const RDF_ABOUT                       = 'about';
  const RDF_ABOUT_EACH                  = 'aboutEach';
  const RDF_ABOUT_EACH_PREFIX           = 'aboutEachPrefix';
  const RDF_BAG_ID                      = 'bagID';
  const RDF_RESOURCE                    = 'resource';
  const RDF_VALUE                       = 'value';
  const RDF_PARSE_TYPE                  = 'parseType';
  const RDF_PARSE_TYPE_LITERAL          = 'Literal';
  const RDF_PARSE_TYPE_RESOURCE         = 'Resource';
  const RDF_TYPE                        = 'type';
  const RDF_BAG                         = 'Bag';
  const RDF_SEQ                         = 'Seq';
  const RDF_ALT                         = 'Alt';
  const RDF_LI                          = 'li';
  const RDF_STATEMENT                   = 'Statement';
  const RDF_SUBJECT                     = 'subject';
  const RDF_PREDICATE                   = 'predicate';
  const RDF_OBJECT                      = 'object';

  const NAMESPACE_SEPARATOR_CHAR        = '^';
  const NAMESPACE_SEPARATOR_STRING      = '^';

  const IN_TOP_LEVEL                    = 0;
  const IN_RDF                          = 1;
  const IN_DESCRIPTION                  = 2;
  const IN_PROPERTY_UNKNOWN_OBJECT      = 3;
  const IN_PROPERTY_RESOURCE            = 4;
  const IN_PROPERTY_EMPTY_RESOURCE      = 5;
  const IN_PROPERTY_LITERAL             = 6;
  const IN_PROPERTY_PARSE_TYPE_LITERAL  = 7;
  const IN_PROPERTY_PARSE_TYPE_RESOURCE = 8;
  const IN_XML                          = 9;
  const IN_UNKNOWN                      = 10;

  const RDF_SUBJECT_TYPE_URI            = 0;
  const RDF_SUBJECT_TYPE_DISTRIBUTED    = 1;
  const RDF_SUBJECT_TYPE_PREFIX         = 2;
  const RDF_SUBJECT_TYPE_ANONYMOUS      = 3;

  const RDF_OBJECT_TYPE_RESOURCE        = 0;
  const RDF_OBJECT_TYPE_LITERAL         = 1;
  const RDF_OBJECT_TYPE_XML             = 2;

  public $rdf_parser;

  // --------------------------------------------------------------------------

  public function rdf_parser_create($encoding) {
    $parser = xml_parser_create_ns($encoding, self::NAMESPACE_SEPARATOR_CHAR);
    xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
    $this->rdf_parser["xml_parser"] = $parser;

    xml_set_object($this->rdf_parser["xml_parser"], $this);
    xml_set_element_handler($this->rdf_parser["xml_parser"], "_start_element_handler", "_end_element_handler");
    xml_set_character_data_handler($this->rdf_parser["xml_parser"], "_character_data_handler");

    return $this->rdf_parser;
  }

  public function rdf_parser_free() {
    $z = 3;
    //    xml_parser_free( $this->rdf_parser["xml_parser"] );
    $this->rdf_parser["base_uri"] = self::EMPTY_STRING;

    $this->_delete_elements($this->rdf_parser);

    unset($this->rdf_parser);
  }

  public function rdf_set_user_data(&$user_data) {
    $this->rdf_parser["user_data"] = & $user_data;
  }

  public function rdf_get_user_data() {
    return ($this->rdf_parser["$user_data"]);
  }

  public function rdf_set_statement_handler($handler) {
    $this->rdf_parser["statement_handler"] = $handler;
  }

  public function rdf_set_parse_type_literal_handler($start, $end) {
    $this->rdf_parser["start_parse_type_literal_handler"] = $start;
    $this->rdf_parser["end_parse_type_literal_handler"] = $end;
  }

  public function rdf_set_element_handler($start, $end) {
    $this->rdf_parser["_start_element_handler"] = $start;
    $this->rdf_parser["_end_element_handler"] = $end;
  }

  public function rdf_set_character_data_handler($handler) {
    $this->rdf_parser["_character_data_handler"] = $handler;
  }

  public function rdf_set_warning_handler($handler) {
    $this->rdf_parser["warning_handler"] = $handler;
  }

  public function rdf_parse($s, $len, $is_final) {
    return XML_Parse($this->rdf_parser["xml_parser"], $s, $is_final);
  }

  public function rdf_get_xml_parser() {
    return ($this->rdf_parser["xml_parser"]);
  }

  public function rdf_set_base($base) {
    /* check for out of memory */
    $this->rdf_parser["base_uri"] = $base;

    return 0;
  }

  public function rdf_get_base() {
    return $this->rdf_parser["base_uri"];
  }

  public function rdf_resolve_uri($uri_reference, &$buffer) {
    _resolve_uri_reference($this->rdf_parser["base_uri"], $uri_reference, $buffer, strlen($buffer));
  }

  // --------------------------------------------------------------------------

  private function _new_element() {
    $e["parent"] = Array(); // Parent is a blank Array
    //$this->clear_element($e["parent"]);
    $e["state"] = 0;
    $e["has_property_atributes"] = 0;
    $e["has_member_attributes"] = 0;
    $e["subject_type"] = 0;
    $e["subject"] = self::EMPTY_STRING;
    $e["predicate"] = self::EMPTY_STRING;
    $e["ordinal"] = 0;
    $e["members"] = 0;
    $e["data"] = self::EMPTY_STRING;
    $e["xml_lang"] = self::EMPTY_STRING;
    $e["bag_id"] = self::EMPTY_STRING;
    $e["statements"] = 0;
    $e["statement_id"] = self::EMPTY_STRING;

    return $e;
  }

  private function _copy_element($source, &$destination) {
    if ($source) {
      $destination["parent"] = $source;
      $destination["state"] = $source["state"];
      $destination["xml_lang"] = $source["xml_lang"];
    }
  }

  private function _clear_element(&$e) {
    $e["subject"] = self::EMPTY_STRING;
    $e["predicate"] = self::EMPTY_STRING;
    $e["data"] = self::EMPTY_STRING;
    $e["bag_id"] = self::EMPTY_STRING;
    $e["statement_id"] = self::EMPTY_STRING;

    if (isset($e["parent"])) {
      if ($e["parent"]) {
        if ($e["parent"]["xml_lang"] != $e["xml_lang"]) {
          $e["xml_lang"] = self::EMPTY_STRING;
        }
      }
      else {
        $e["xml_lang"] = self::EMPTY_STRING;
      }
    }
    else {
      $e["xml_lang"] = self::EMPTY_STRING;
    }

    //memset( e, 0, strlen( _rdf_element ) );
    $e["parent"] = Array();
    $e["state"] = 0;
    $e["has_property_attributes"] = 0;
    $e["has_member_attributes"] = 0;
    $e["subject_type"] = 0;
    $e["subject"] = self::EMPTY_STRING;
    $e["predicate"] = self::EMPTY_STRING;
    $e["ordinal"] = 0;
    $e["members"] = 0;
    $e["data"] = self::EMPTY_STRING;
    $e["xml_lang"] = self::EMPTY_STRING;
    $e["bag_id"] = self::EMPTY_STRING;
    $e["statements"] = 0;
    $e["statement_id"] = self::EMPTY_STRING;

  }

  private function _push_element() {
    if (!isset($this->rdf_parser["free"])) {
      $this->rdf_parser["free"] = Array();
    }

    if (count($this->rdf_parser["free"]) > 0) {
      $e = $this->rdf_parser["free"];
      if (isset($e["parent"])) {
        $this->rdf_parser["free"] = $e["parent"];
      }
      else {
        $this->rdf_parser["free"] = $this->_new_element();
      }
    }
    else {
      $e = $this->_new_element();
    }

    if (!isset($this->rdf_parser["top"])) {
      $this->rdf_parser["top"] = Array();
    }

    $this->_copy_element($this->rdf_parser["top"], $e);
    $this->rdf_parser["top"] = $e;
  }

  private function _pop_element() {
    $e = $this->rdf_parser["top"];
    $this->rdf_parser["top"] = $e["parent"];
    $this->_clear_element($e);
    $this->rdf_parser["free"] = $e;
  }

  private function _delete_elements() {
  }

  private function _is_rdf_property_attribute_resource($local_name) {
    return ($local_name == self::RDF_TYPE);
  }

  private function _is_rdf_property_attribute_literal($local_name) {
    return ($local_name == self::RDF_VALUE);
  }

  private function _is_rdf_ordinal($local_name) {
    $ordinal = - 1;

    if ($local_name[0] == self::UNDERSCORE) {
      $ordinal = substr($local_name, 1) + 1;
    }

    return ($ordinal > 0) ? $ordinal : 0;
  }

  private function _is_rdf_property_attribute($local_name) {
    return $this->_is_rdf_property_attribute_resource($local_name) || $this->_is_rdf_property_attribute_literal($local_name);
  }

  private function _is_rdf_property_element($local_name) {
    return
      ($local_name == self::RDF_TYPE) || ($local_name == self::RDF_SUBJECT) || ($local_name == self::RDF_PREDICATE) ||
      ($local_name == self::RDF_OBJECT) || ($local_name == self::RDF_VALUE) || ($local_name == self::RDF_LI) ||
      ($local_name[0] == self::UNDERSCORE);
  }

  private function _istalnum($val) {
    return preg_match("/[A-Za-z0-9]/", $val);
  }

  private function _istalpha($val) {
    return preg_match("/[A-Za-z]/", $val);
  }

  private function _is_absolute_uri($uri) {
    $result = false;
    $uri_p = 0;
    if ($uri && $this->_istalpha($uri[$uri_p])) {
      ++$uri_p;

    while (($uri_p < strlen($uri)) && ($this->_istalnum($uri[$uri_p]) || ($uri[$uri_p] == '+') || ($uri[$uri_p] == self::DASH) || ($uri[$uri_p] == self::DOT))) {
        ++$uri_p;
      }

      $result = ($uri[$uri_p] == self::COLON);
    }
    return $result;
  }

  /*
  This function returns an associative array returning any of the various components of the URL that are present. This includes the
  $arr=parse_url($url)
  scheme - e.g. http
  host
  port
  user
  pass
  path
  query - after the question mark ?
  fragment - after the hashmark #
  */
  private function _parse_uri($uri, $buffer, $len, &$scheme, &$authority, &$path, &$query, &$fragment) {
    $parsed = parse_url($uri);
    if (isset($parsed["scheme"])) {
      $scheme = $parsed["scheme"];
    }
    else {
      $scheme = self::EMPTY_STRING;
    }

    if (isset($parsed["host"])) {
      $host = $parsed["host"];
    }
    else {
      $host = self::EMPTY_STRING;
    }

    if (isset($parsed["host"])) {
      $authority = $parsed["host"];
    }
    else {
      $authority = self::EMPTY_STRING;
    }

    if (isset($parsed["path"])) {
      $path = $parsed["path"];
    }
    else {
      $path = self::EMPTY_STRING;
    }

    if (isset($parsed["query"])) {
      $query = $parsed["query"];
    }
    else {
      $query = self::EMPTY_STRING;
    }

    if (isset($parsed["fragment"])) {
      $fragment = $parsed["fragment"];
    }
    else {
      $fragment = self::EMPTY_STRING;
    }
  }

  private function _resolve_uri_reference($base_uri, $reference_uri, &$buffer, $length) {
    $base_buffer = self::EMPTY_STRING;
    $reference_buffer = self::EMPTY_STRING;
    $path_buffer = self::EMPTY_STRING;

    $buffer = self::EMPTY_STRING;

    $this->_parse_uri($reference_uri, $reference_buffer, strlen($reference_buffer) , $reference_scheme, $reference_authority, $reference_path, $reference_query, $reference_fragment);

    if ($reference_scheme == self::EMPTY_STRING && $reference_authority == self::EMPTY_STRING && $reference_path == self::EMPTY_STRING && $reference_query == self::EMPTY_STRING) {
      $buffer = $base_uri;

      if ($reference_fragment != self::EMPTY_STRING) {
        $buffer .= "#";
        $buffer .= $reference_fragment;
      }
    }
    elseif ($reference_scheme != self::EMPTY_STRING) {
      $buffer = $reference_uri;
    }
    else {
      $this->_parse_uri($base_uri, $base_buffer, strlen($base_buffer) , $base_scheme, $base_authority, $base_path, $base_query, $base_fragment);

      $result_scheme = $base_scheme;

      if ($reference_authority != self::EMPTY_STRING) {
        $result_authority = $reference_authority;
      }
      else {
        $result_authority = $base_authority;

        if ($reference_path != self::EMPTY_STRING && (($reference_path[0] == '/') || ($reference_path[0] == '\\'))) {
          $result_path = $reference_path;
        }
        else {
          $p = self::EMPTY_STRING;

          $result_path = $path_buffer;

          $path_buffer = self::EMPTY_STRING;

          $p = strstr($base_path, '/');

          if (!$p) {
            $p = strstr($base_path, '\\');
          }

          if ($p) {

            $path_buffer .= $base_path;

            //while( s <= p )
            //{
            //  *d++ = *s++;
            //}
            //*d++ = 0;
            
          }

          if ($reference_path != self::EMPTY_STRING) {
            $path_buffer .= $reference_path;
          }

          //remove all occurrences of "./"
          //print($path_buffer);
          $path_buffer = preg_replace("/\/\.\//", "/", $path_buffer);
          $path_buffer = preg_replace("/\/([^\/\.])*\/..$/", "/", $path_buffer);

          while (preg_match("/\.\./", $path_buffer)) {
            $path_buffer = preg_replace("/\/([^\/\.]*)\/..\//", "/", $path_buffer);
          }

          $path_buffer = preg_replace("/\.$/", "", $path_buffer);

        }
      }

      // This replaces the C pointer assignament
      $result_path = $path_buffer;
      if ($result_scheme != self::EMPTY_STRING) {
        $buffer = $result_scheme;
        $buffer .= ":";
      }

      if ($result_authority != self::EMPTY_STRING) {
        $buffer .= "//";
        $buffer .= $result_authority;
      }

      if ($result_path != self::EMPTY_STRING) {

        $buffer .= $result_path;
      }

      if ($reference_query != self::EMPTY_STRING) {
        $buffer .= "?";
        $buffer .= $reference_query;
      }

      if ($reference_fragment != self::EMPTY_STRING) {
        $buffer .= "#";
        $buffer .= $reference_fragment;
      }
    }
  }

  private function is_valid_id($id) {
    $result = false;
    $p = $id;
    $p_p = 0;

    if ($id != self::EMPTY_STRING) {
      if ($this->_istalpha($p) || $p[0] == self::UNDERSCORE || $p[0] == self::COLON) {
        $result = true;

        while ($result != false && ($p[++$p_p] != 0)) {
          if (!($this->_istalnum($p[$p_p]) || $p[$p_p] == self::DOT || $p[$p_p] == self::DASH || $p[$p_p] == self::UNDERSCORE || $p[$p_p] == self::COLON)) {
            $result = false;
          }
        }
      }
    }

    return $result;
  }

  private function _resolve_id($id, &$buffer, $length) {
    $id_buffer = self::EMPTY_STRING;

    if ($this->is_valid_id($id) == true) {
      $id_buffer = "#$id";
    }
    else {
      $this->report_warning("bad ID attribute: " . $id_buffer . "#_bad_ID_attribute_");
    }

    $this->_resolve_uri_reference($this->rdf_parser["base_uri"], $id_buffer, $buffer, $length);
  }

  private function _split_name($name, &$buffer, $len, &$namespace_uri, &$local_name) {

    static $nul = 0;
    $buffer = $name;

    if (strstr($buffer, self::NAMESPACE_SEPARATOR_CHAR)) {
      $cosas = explode(self::NAMESPACE_SEPARATOR_CHAR, $buffer);
      $namespace_uri = $cosas[0];
      $local_name = $cosas[1];
    }
    else {
      if (($buffer[0] == 'x') && ($buffer[1] == 'm') && ($buffer[2] == 'l') && ($buffer[3] == self::COLON)) {
        $namespace_uri = self::XML_NAMESPACE_URI;
        $local_name = substr($buffer, 4);
      }
      else {
        $namespace_uri = self::EMPTY_STRING;
        $local_name = $buffer;
      }
    }

  }

  private function _generate_anonymous_uri(&$buf, $len) {
    $id = self::EMPTY_STRING;
    if (!isset($this->rdf_parser["anonymous_id"])) {
      $this->rdf_parser["anonymous_id"] = 0;
    }
    $this->rdf_parser["anonymous_id"]++;

    $id = "#genid" . $this->rdf_parser["anonymous_id"];
    $this->_resolve_uri_reference($this->rdf_parser["base_uri"], $id, $buf, $len);

  }

  private function _report_statement($subject_type, $subject, $predicate, $ordinal, $object_type, $object, $xml_lang, $bag_id, $statements, $statement_id) {
    $statement_id_type = self::RDF_SUBJECT_TYPE_URI;
    $statement_id_buffer = self::EMPTY_STRING;
    $predicate_buffer = self::EMPTY_STRING;

    if ($this->rdf_parser["statement_handler"]) {
      $this->rdf_parser["user_data"] = call_user_func_array($this->rdf_parser["statement_handler"], array(&$this->rdf_parser["user_data"], $subject_type, $subject, $predicate, $ordinal, $object_type, $object, $xml_lang));
      // $this->rdf_parser["statement_handler"]($this->rdf_parser["user_data"],$subject_type,$subject,$predicate,$ordinal,$object_type,$object,$xml_lang )
      if ($bag_id) {
        if ($statements == self::EMPTY_STRING) {
          $this->_report_statement(self::RDF_SUBJECT_TYPE_URI, $bag_id, self::RDF_NAMESPACE_URI . self::RDF_TYPE, 0, self::RDF_OBJECT_TYPE_RESOURCE, self::RDF_NAMESPACE_URI . self::RDF_BAG, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING);
        }

        if (!$statement_id) {
          $statement_id_type = self::RDF_SUBJECT_TYPE_ANONYMOUS;
          $this->_generate_anonymous_uri($statement_id_buffer, strlen($statement_id_buffer));
          $statement_id = $statement_id_buffer;
        }
        $statements++;
        $predicate_buffer = "self::RDF_NAMESPACE_URI_" . $statements;

        $this->_report_statement(self::RDF_SUBJECT_TYPE_URI, $bag_id, $predicate_buffer, $statements, self::RDF_OBJECT_TYPE_RESOURCE, $statement_id, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING);
      }

      if ($statement_id) {
        // rdf:type = rdf:Statement
        $this->_report_statement(
          $statement_id_type,
          $statement_id,
          self::RDF_NAMESPACE_URI . self::RDF_TYPE,
          0,
          self::RDF_OBJECT_TYPE_RESOURCE,
          self::RDF_NAMESPACE_URI . self::RDF_STATEMENT,
          self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING
        );

        // rdf:subject
        $this->_report_statement(
          $statement_id_type,
          $statement_id,
          self::RDF_NAMESPACE_URI . self::RDF_SUBJECT,
          0,
          self::RDF_OBJECT_TYPE_RESOURCE,
          $subject,
          self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING
        );

        // rdf:predicate
        $this->_report_statement(
          $statement_id_type,
          $statement_id,
          self::RDF_NAMESPACE_URI . self::RDF_PREDICATE,
          0,
          self::RDF_OBJECT_TYPE_RESOURCE,
          $predicate,
          self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING
        );

        // rdf:object
        $this->_report_statement(
          $statement_id_type,
          $statement_id,
          self::RDF_NAMESPACE_URI . self::RDF_OBJECT,
          0,
          $object_type,
          $object,
          self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING, self::EMPTY_STRING
        );
      }
    }
  }

  private function _report_start_parse_type_literal() {
    if ($this->rdf_parser["start_parse_type_literal_handler"]) {
      $this->rdf_parser["start_parse_type_literal_handler"]($this->rdf_parser["user_data"]);
    }
  }

  private function _report_end_parse_type_literal() {
    if ($this->rdf_parser["end_parse_type_literal_handler"]) {
      $this->rdf_parser["end_parse_type_literal_handler"]($this->rdf_parser["user_data"]);
    }
  }

  private function _handle_property_attributes($subject_type, $subject, $attributes, $xml_lang, $bag_id, $statements) {
    $i = 0;

    $attribute = self::EMPTY_STRING;
    $predicate = self::EMPTY_STRING;

    $attribute_namespace_uri = self::EMPTY_STRING;
    $attribute_local_name = self::EMPTY_STRING;
    $attribute_value = self::EMPTY_STRING;

    $ordinal = 0;

    for ($i = 0;isset($attributes[$i]);$i += 2) {
      $this->_split_name($attributes[$i], $attribute, strlen($attribute) , $attribute_namespace_uri, $attribute_local_name);

      $attribute_value = $attributes[$i + 1];

      $predicate = $attribute_namespace_uri;
      $predicate .= $attribute_local_name;

      if (self::RDF_NAMESPACE_URI == $attribute_namespace_uri) {
        if ($this->_is_rdf_property_attribute_literal($attribute_local_name)) {
          $this->_report_statement($subject_type, $subject, $predicate, 0, self::RDF_OBJECT_TYPE_LITERAL, $attribute_value, $xml_lang, $bag_id, $statements, self::EMPTY_STRING);
        }
        elseif ($this->_is_rdf_property_attribute_resource($attribute_local_name)) {
          $this->_report_statement($subject_type, $subject, $predicate, 0, self::RDF_OBJECT_TYPE_RESOURCE, $attribute_value, self::EMPTY_STRING, $bag_id, $statements, self::EMPTY_STRING);
        }
        elseif (($ordinal = $this->_is_rdf_ordinal($attribute_local_name)) != 0) {
          $this->_report_statement($subject_type, $subject, $predicate, $ordinal, self::RDF_OBJECT_TYPE_LITERAL, $attribute_value, $xml_lang, $bag_id, $statements, self::EMPTY_STRING);
        }
      }
      elseif (self::XML_NAMESPACE_URI == $attribute_namespace_uri) {
        //do nothing
      }
      elseif ($attribute_namespace_uri) {
        // is it required that property attributes be in an explicit namespace?
        $this->_report_statement($subject_type, $subject, $predicate, 0, self::RDF_OBJECT_TYPE_LITERAL, $attribute_value, $xml_lang, $bag_id, $statements, self::EMPTY_STRING);
      }
    }
  }

  private function _report_start_element($name, $attributes) {
    if (isset($this->rdf_parser["start_element_handler"])) {
      $this->rdf_parser["start_element_handler"]($this->rdf_parser["user_data"], $name, $attributes);
    }
  }

  private function _report_end_element($name) {
    if (isset($this->rdf_parser["end_element_handler"])) {
      $this->rdf_parser["end_element_handler"]($this->rdf_parser["user_data"], $name);
    }
  }

  private function _report_character_data($s, $len) {
    if (isset($this->rdf_parser["character_data_handler"])) {
      $this->rdf_parser["character_data_handler"]($this->rdf_parser["user_data"], $s, $len);
    }
  }

  private function _report_warning($warning) {
    // rdf_parser->top->state = self::IN_UNKNOWN;
    if (isset($this->rdf_parser["warning_handler"])) {
      $this->rdf_parser["warning_handler"]($warning);
    }
  }

  private function _handle_resource_element($namespace_uri, $local_name, $attributes, $parent) {
    $subjects_found = 0;
    $aux = $attributes;
    $aux2 = Array();

    foreach ($attributes as $atkey => $atvalue) {
      $aux2[] = $atkey;
      $aux2[] = $atvalue;
    }

    $attributes = $aux2;
    $id = self::EMPTY_STRING;
    $about = self::EMPTY_STRING;
    $about_each = self::EMPTY_STRING;
    $about_each_prefix = self::EMPTY_STRING;

    $bag_id = self::EMPTY_STRING;

    $i = 0;

    $attribute = self::EMPTY_STRING;

    $attribute_namespace_uri = self::EMPTY_STRING;
    $attribute_local_name = self::EMPTY_STRING;
    $attribute_value = self::EMPTY_STRING;

    $id_buffer = self::EMPTY_STRING;

    $type = self::EMPTY_STRING;

    $this->rdf_parser["top"]["has_property_attributes"] = false;
    $this->rdf_parser["top"]["has_member_attributes"] = false;

    // examine each attribute for the standard RDF "keywords"
    for ($i = 0;isset($attributes[$i]);$i += 2) {
      $this->_split_name($attributes[$i], $attribute, strlen($attribute) , $attribute_namespace_uri, $attribute_local_name);

      $attribute_value = $attributes[$i + 1];

      // if the attribute is not in any namespace
      //   or the attribute is in the RDF namespace
      if (($attribute_namespace_uri == self::EMPTY_STRING) || ($attribute_namespace_uri == self::RDF_NAMESPACE_URI)) {
        if ($attribute_local_name == self::RDF_ID) {
          $id = $attribute_value;
          ++$subjects_found;
        }
        elseif ($attribute_local_name == self::RDF_ABOUT) {
          $about = $attribute_value;
          ++$subjects_found;
        }
        elseif ($attribute_local_name == self::RDF_ABOUT_EACH) {
          $about_each = $attribute_value;
          ++$subjects_found;
        }
        elseif ($attribute_local_name == self::RDF_ABOUT_EACH_PREFIX) {
          $about_each_prefix = $attribute_value;
          ++$subjects_found;
        }
        elseif ($attribute_local_name == self::RDF_BAG_ID) {
          $bag_id = $attribute_value;
        }
        elseif ($this->_is_rdf_property_attribute($attribute_local_name)) {
          $this->rdf_parser["top"]["has_property_attributes"] = true;
        }
        elseif ($this->_is_rdf_ordinal($attribute_local_name)) {
          $this->rdf_parser["top"]["has_property_attributes"] = true;
          $this->rdf_parser["top"]["has_member_attributes"] = true;
        }
        else {
          $this->_report_warning("unknown or out of context rdf attribute:" . $attribute_local_name);
        }
      }
      elseif ($attribute_namespace_uri == self::XML_NAMESPACE_URI) {
        if ($attribute_local_name == self::XML_LANG) {
          $this->rdf_parser["top"]["xml_lang"] = $attribute_value;
        }
      }
      elseif ($attribute_namespace_uri) {
        $this->rdf_parser["top"]["has_property_attributes"] = true;
      }
    }

    // if no subjects were found, generate one.
    if ($subjects_found == 0) {
      $this->_generate_anonymous_uri($id_buffer, strlen($id_buffer));
      $this->rdf_parser["top"]["subject"] = $id_buffer;
      $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_ANONYMOUS;
    }
    elseif ($subjects_found > 1) {
      $this->_report_warning("ID, about, aboutEach, and aboutEachPrefix are mutually exclusive");
      return;
    }
    elseif ($id) {
      $this->_resolve_id($id, $id_buffer, strlen($id_buffer));
      $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_URI;
      $this->rdf_parser["top"]["subject"] = $id_buffer;
    }
    elseif ($about) {
      $this->_resolve_uri_reference($this->rdf_parser["base_uri"], $about, $id_buffer, strlen($id_buffer));
      $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_URI;
      $this->rdf_parser["top"]["subject"] = $id_buffer;
    }
    elseif ($about_each) {
      $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_DISTRIBUTED;
      $this->rdf_parser["top"]["subject"] = $about_each;
    }
    elseif ($about_each_prefix) {
      $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_PREFIX;
      $this->rdf_parser["top"]["subject"] = $about_each_prefix;
    }

    // if the subject is empty, assign it the document uri
    if ($this->rdf_parser["top"]["subject"] == self::EMPTY_STRING) {
      $len = 0;

      $this->rdf_parser["top"]["subject"] = $this->rdf_parser["base_uri"];

      // now remove the trailing '#'
      $len = strlen($this->rdf_parser["top"]["subject"]);
    }

    if ($bag_id) {
      $this->_resolve_id($bag_id, $id_buffer, strlen($id_buffer));
      $this->rdf_parser["top"]["bag_id"] = $id_buffer;
    }

    // only report the type for non-rdf:Description elements.
    if (($local_name != self::RDF_DESCRIPTION) || ($namespace_uri != self::RDF_NAMESPACE_URI)) {
      $type = $namespace_uri;
      $type .= $local_name;

      $this->_report_statement(
        $this->rdf_parser["top"]["subject_type"],
        $this->rdf_parser["top"]["subject"],
        self::RDF_NAMESPACE_URI . self::RDF_TYPE,
        0,
        self::RDF_OBJECT_TYPE_RESOURCE,
        $type,
        self::EMPTY_STRING,
        $this->rdf_parser["top"]["bag_id"],
        $this->rdf_parser["top"]["statements"],
        self::EMPTY_STRING
      );

    }

    // if this element is the child of some property,
    //   report the appropriate statement.
    if ($parent) {
      $this->_report_statement(
        $parent["parent"]["subject_type"],
        $parent["parent"]["subject"],
        $parent["predicate"],
        $parent["ordinal"],
        self::RDF_OBJECT_TYPE_RESOURCE,
        $this->rdf_parser["top"]["subject"],
        self::EMPTY_STRING,
        $parent["parent"]["bag_id"],
        $parent["parent"]["statements"],
        $parent["statement_id"]
      );
    }

    if ($this->rdf_parser["top"]["has_property_attributes"]) {
      $this->_handle_property_attributes(
        $this->rdf_parser["top"]["subject_type"],
        $this->rdf_parser["top"]["subject"],
        $attributes,
        $this->rdf_parser["top"]["xml_lang"],
        $this->rdf_parser["top"]["bag_id"],
        $this->rdf_parser["top"]["statements"]
      );
    }
  }

  private function _handle_property_element(&$namespace_uri, &$local_name, &$attributes) {
    $buffer = self::EMPTY_STRING;

    $i = 0;

    $aux = $attributes;
    $aux2 = Array();

    foreach ($attributes as $atkey => $atvalue) {
      $aux2[] = $atkey;
      $aux2[] = $atvalue;
    }

    $attributes = $aux2;

    $attribute_namespace_uri = self::EMPTY_STRING;
    $attribute_local_name = self::EMPTY_STRING;
    $attribute_value = self::EMPTY_STRING;

    $resource = self::EMPTY_STRING;
    $statement_id = self::EMPTY_STRING;
    $bag_id = self::EMPTY_STRING;
    $parse_type = self::EMPTY_STRING;

    $this->rdf_parser["top"]["ordinal"] = 0;

    if ($namespace_uri == self::RDF_NAMESPACE_URI) {
      if (($this->rdf_parser["top"]["ordinal"] = ($this->_is_rdf_ordinal($local_name)) != 0)) {
        if ($this->rdf_parser["top"]["ordinal"] > $this->rdf_parser["top"]["parent"]["members"]) {
          $this->rdf_parser["top"]["parent"]["members"] = $this->rdf_parser["top"]["ordinal"];
        }
      }
      elseif (!$this->_is_rdf_property_element($local_name)) {
        $this->_report_warning("unknown or out of context rdf property element: " . $local_name);
        return;
      }
    }

    $buffer = $namespace_uri;

    if (($namespace_uri == self::RDF_NAMESPACE_URI) && ($local_name == self::RDF_LI)) {
      //$ordinal=self::EMPTY_STRING;
      $this->rdf_parser["top"]["parent"]["members"]++;
      $this->rdf_parser["top"]["ordinal"] = $this->rdf_parser["top"]["parent"]["members"];

      $this->rdf_parser["top"]["ordinal"] = $this->rdf_parser["top"]["ordinal"];
      //$ordinal{ 0 } =  self::UNDERSCORE ;
      $buffer .= self::UNDERSCORE . $this->rdf_parser["top"]["ordinal"];
    }
    else {
      $buffer .= $local_name;
    }

    $this->rdf_parser["top"]["predicate"] = $buffer;

    $this->rdf_parser["top"]["has_property_attributes"] = false;
    $this->rdf_parser["top"]["has_member_attributes"] = false;

    for ($i = 0;isset($attributes[$i]);$i += 2) {
      $this->_split_name($attributes[$i], $buffer, strlen($buffer) , $attribute_namespace_uri, $attribute_local_name);

      $attribute_value = $attributes[$i + 1];

      // if the attribute is not in any namespace
      //   or the attribute is in the RDF namespace
      if (($attribute_namespace_uri == self::EMPTY_STRING) || ($attribute_namespace_uri == self::RDF_NAMESPACE_URI)) {
        if (($attribute_local_name == self::RDF_ID)) {
          $statement_id = $attribute_value;
        }
        elseif ($attribute_local_name == self::RDF_PARSE_TYPE) {
          $parse_type = $attribute_value;
        }
        elseif ($attribute_local_name == self::RDF_RESOURCE) {
          $resource = $attribute_value;
        }
        elseif ($attribute_local_name == self::RDF_BAG_ID) {
          $bag_id = $attribute_value;
        }
        elseif ($this->_is_rdf_property_attribute($attribute_local_name)) {
          $this->rdf_parser["top"]["has_property_attributes"] = true;
        }
        else {
          $this->_report_warning("unknown rdf attribute: " . $attribute_local_name);
          return;
        }
      }
      elseif ($attribute_namespace_uri == self::XML_NAMESPACE_URI) {
        if ($attribute_local_name == self::XML_LANG) {
          $this->rdf_parser["top"]["xml_lang"] = $attribute_value;
        }
      }
      elseif ($attribute_namespace_uri) {
        $this->rdf_parser["top"]["has_property_attributes"] = true;
      }
    }

    // this isn't allowed by the M&S but I think it should be
    if ($statement_id && $resource) {
      $this->_report_warning("rdf:ID and rdf:resource are mutually exclusive");
      return;
    }

    if ($statement_id) {
      $this->_resolve_id($statement_id, $buffer, strlen($buffer));
      $this->rdf_parser["top"]["statement_id"] = $buffer;
    }

    if ($parse_type) {
      if ($resource) {
        $this->_report_warning("property elements with rdf:parseType do not allow rdf:resource");
        return;
      }

      if ($bag_id) {
        $this->_report_warning("property elements with rdf:parseType do not allow rdf:bagID");
        return;
      }

      if ($this->rdf_parser["top"]["has_property_attributes"]) {
        $this->_report_warning("property elements with rdf:parseType do not allow property attributes");
        return;
      }

      if ($attribute_value == self::RDF_PARSE_TYPE_RESOURCE) {
        $this->_generate_anonymous_uri($buffer, strlen($buffer));

        // since we are sure that this is now a resource property we can report it
        $this->_report_statement(
          $this->rdf_parser["top"]["parent"]["subject_type"],
          $this->rdf_parser["top"]["parent"]["subject"],
          $this->rdf_parser["top"]["predicate"],
          0,
          self::RDF_OBJECT_TYPE_RESOURCE,
          $buffer,
          self::EMPTY_STRING,
          $this->rdf_parser["top"]["parent"]["bag_id"],
          $this->rdf_parser["top"]["parent"]["statements"],
          $statement_id
        );

        $this->_push_element();

        $this->rdf_parser["top"]["state"] = self::IN_PROPERTY_PARSE_TYPE_RESOURCE;
        $this->rdf_parser["top"]["subject_type"] = self::RDF_SUBJECT_TYPE_ANONYMOUS;
        $this->rdf_parser["top"]["subject"] = $buffer;
        $this->rdf_parser["top"]["bag_id"] = self::EMPTY_STRING;
      }
      else {
        $this->_report_statement(
          $this->rdf_parser["top"]["parent"]["subject_type"],
          $this->rdf_parser["top"]["parent"]["subject"],
          $this->rdf_parser["top"]["predicate"],
          0,
          self::RDF_OBJECT_TYPE_XML,
          self::EMPTY_STRING,
          self::EMPTY_STRING,
          $this->rdf_parser["top"]["parent"]["bag_id"],
          $this->rdf_parser["top"]["parent"]["statements"],
          $statement_id
        );

        $this->rdf_parser["top"]["state"] = self::IN_PROPERTY_PARSE_TYPE_LITERAL;
        $this->_report_start_parse_type_literal();
      }
    }
    elseif ($resource || $bag_id || $this->rdf_parser["top"]["has_property_attributes"]) {
      if ($resource != self::EMPTY_STRING) {
        $subject_type = self::RDF_SUBJECT_TYPE_URI;
        $this->_resolve_uri_reference($this->rdf_parser["base_uri"], $resource, $buffer, strlen($buffer));
      }
      else {
        $subject_type = self::RDF_SUBJECT_TYPE_ANONYMOUS;
        $this->_generate_anonymous_uri($buffer, strlen($buffer));
      }

      $this->rdf_parser["top"]["state"] = self::IN_PROPERTY_EMPTY_RESOURCE;

      // since we are sure that this is now a resource property we can report it.
      $this->_report_statement(
        $this->rdf_parser["top"]["parent"]["subject_type"],
        $this->rdf_parser["top"]["parent"]["subject"],
        $this->rdf_parser["top"]["predicate"],
        $this->rdf_parser["top"]["ordinal"],
        self::RDF_OBJECT_TYPE_RESOURCE,
        $buffer,
        self::EMPTY_STRING,
        $this->rdf_parser["top"]["parent"]["bag_id"],
        $this->rdf_parser["top"]["parent"]["statements"],
        self::EMPTY_STRING
      ); // should we allow IDs?

      if ($bag_id) {
        $this->_resolve_id($bag_id, $buffer, strlen($buffer));
        $this->rdf_parser["top"]["bag_id"] = $buffer;
      }

      if ($this->rdf_parser["top"]["has_property_attributes"]) {
        $this->_handle_property_attributes(
          $subject_type,
          $buffer,
          $attributes,
          $this->rdf_parser["top"]["xml_lang"],
          $this->rdf_parser["top"]["bag_id"],
          $this->rdf_parser["top"]["statements"]
        );
      }
    }
  }

  private function _start_element_handler($parser, $name, $attributes) {
    $buffer = self::EMPTY_STRING;

    $namespace_uri = self::EMPTY_STRING;
    $local_name = self::EMPTY_STRING;

    $this->_push_element();

    $this->_split_name($name, $buffer, strlen($buffer) , $namespace_uri, $local_name);

    switch ($this->rdf_parser["top"]["state"]) {
      case self::IN_TOP_LEVEL:
        if (self::RDF_NAMESPACE_URI . self::NAMESPACE_SEPARATOR_STRING . self::RDF_RDF == $name) {
          $this->rdf_parser["top"]["state"] = self::IN_RDF;
        }
        else {
          $this->_report_start_element($name, $attributes);
        }
      break;
      case self::IN_RDF:
        $this->rdf_parser["top"]["state"] = self::IN_DESCRIPTION;
        $this->_handle_resource_element($namespace_uri, $local_name, $attributes, self::EMPTY_STRING);
      break;
      case self::IN_DESCRIPTION:
      case self::IN_PROPERTY_PARSE_TYPE_RESOURCE:
        $this->rdf_parser["top"]["state"] = self::IN_PROPERTY_UNKNOWN_OBJECT;
        $this->_handle_property_element($namespace_uri, $local_name, $attributes);
      break;
      case self::IN_PROPERTY_UNKNOWN_OBJECT:
        /* if we're in a property with an unknown object type and we encounter
         an element, the object must be a resource, */
        $this->rdf_parser["top"]["data"] = self::EMPTY_STRING;
        $this->rdf_parser["top"]["parent"]["state"] = self::IN_PROPERTY_RESOURCE;
        $this->rdf_parser["top"]["state"] = self::IN_DESCRIPTION;
        $this->_handle_resource_element(
          $namespace_uri,
          $local_name,
          $attributes,
          $this->rdf_parser["top"]["parent"]
        );
      break;
      case self::IN_PROPERTY_LITERAL:
        $this->_report_warning("no markup allowed in literals");
      break;
      case self::IN_PROPERTY_PARSE_TYPE_LITERAL:
        $this->rdf_parser["top"]["state"] = self::IN_XML;
        /* fall through */
      case self::IN_XML:
        $this->_report_start_element($name, $attributes);
      break;
      case self::IN_PROPERTY_RESOURCE:
        $this->_report_warning("only one element allowed inside a property element");
      break;
      case self::IN_PROPERTY_EMPTY_RESOURCE:
        $this->_report_warning("no content allowed in property with rdf:resource, rdf:bagID, or property attributes");
      break;
      case self::IN_UNKNOWN:
      break;
    }
  }

  /*
  this is only called when we're in the self::IN_PROPERTY_UNKNOWN_OBJECT state.
  the only time we won't know what type of object a statement has is
  when we encounter property statements without property attributes or
  content:
  
      <foo:property />
      <foo:property ></foo:property>
      <foo:property>    </foo:property>
  
  notice that the state doesn't switch to self::IN_PROPERTY_LITERAL when
  there is only whitespace between the start and end tags. this isn't
  a very useful statement since the object is anonymous and can't
  have any statements with it as the subject but it is allowed.
  */

  private function _end_empty_resource_property() {
    $buffer = self::EMPTY_STRING;

    $this->_generate_anonymous_uri($buffer, strlen($buffer));

    $this->_report_statement(
      $this->rdf_parser["top"]["parent"]["subject_type"],
      $this->rdf_parser["top"]["parent"]["subject"],
      $this->rdf_parser["top"]["predicate"],
      $this->rdf_parser["top"]["ordinal"],
      self::RDF_OBJECT_TYPE_RESOURCE,
      $buffer, $this->rdf_parser["top"]["xml_lang"],
      $this->rdf_parser["top"]["parent"]["bag_id"],
      $this->rdf_parser["top"]["parent"]["statements"],
      $this->rdf_parser["top"]["statement_id"]
    );
  }

  /*
  property elements with text only as content set the state to
  self::IN_PROPERTY_LITERAL. as character data is received from expat,
  it is saved in a buffer and reported when the end tag is
  received.
  */
  private function _end_literal_property() {
    if (!isset($this->rdf_parser["top"]["statement_id"])) {
      $this->rdf_parser["top"]["statement_id"] = self::EMPTY_STRING;
    }
    if (!isset($this->rdf_parser["top"]["parent"]["subject_type"])) {
      $this->rdf_parser["top"]["parent"]["subject_type"] = self::EMPTY_STRING;
    }
    if (!isset($this->rdf_parser["top"]["parent"]["subject"])) {
      $this->rdf_parser["top"]["parent"]["subject"] = self::EMPTY_STRING;
    }
    if (!isset($this->rdf_parser["top"]["parent"]["bag_id"])) {
      $this->rdf_parser["top"]["parent"]["bag_id"] = self::EMPTY_STRING;
    }
    if (!isset($this->rdf_parser["top"]["parent"]["statements"])) {
      $this->rdf_parser["top"]["parent"]["statements"] = 0;
    }
    if (!isset($this->rdf_parser["top"]["predicate"])) {
      $this->rdf_parser["top"]["predicate"] = self::EMPTY_STRING;
    }
    if (!isset($this->rdf_parser["top"]["ordinal"])) {
      $this->rdf_parser["top"]["ordinal"] = 0;
    }
    $this->_report_statement(
      $this->rdf_parser["top"]["parent"]["subject_type"],
      $this->rdf_parser["top"]["parent"]["subject"],
      $this->rdf_parser["top"]["predicate"],
      $this->rdf_parser["top"]["ordinal"],
      self::RDF_OBJECT_TYPE_LITERAL,
      $this->rdf_parser["top"]["data"],
      $this->rdf_parser["top"]["xml_lang"],
      $this->rdf_parser["top"]["parent"]["bag_id"],
      $this->rdf_parser["top"]["parent"]["statements"],
      $this->rdf_parser["top"]["statement_id"]
    );
  }

  private function _end_element_handler($parser, $name) {

    switch ($this->rdf_parser["top"]["state"]) {
      case self::IN_TOP_LEVEL:
        /* fall through */
      case self::IN_XML:
        $this->_report_end_element($name);
      break;
      case self::IN_PROPERTY_UNKNOWN_OBJECT:
        $this->_end_empty_resource_property();
      break;
      case self::IN_PROPERTY_LITERAL:
        $this->_end_literal_property();
      break;
      case self::IN_PROPERTY_PARSE_TYPE_RESOURCE:
        $this->_pop_element();
      break;
      case self::IN_PROPERTY_PARSE_TYPE_LITERAL:
        $this->_report_end_parse_type_literal();
      break;
      case self::IN_RDF:
      case self::IN_DESCRIPTION:
      case self::IN_PROPERTY_RESOURCE:
      case self::IN_PROPERTY_EMPTY_RESOURCE:
      case self::IN_UNKNOWN:
      break;
    }

    $this->_pop_element();
  }

  private function _character_data_handler($parser, $s) {
    $len = strlen($s);
    switch ($this->rdf_parser["top"]["state"]) {
      case self::IN_PROPERTY_LITERAL:
      case self::IN_PROPERTY_UNKNOWN_OBJECT:
        if (isset($this->rdf_parser["top"]["data"])) {
          $n = strlen($this->rdf_parser["top"]["data"]);
          $this->rdf_parser["top"]["data"] .= $s;

        }
        else {
          $this->rdf_parser["top"]["data"] = $s;
        }

        if ($this->rdf_parser["top"]["state"] == self::IN_PROPERTY_UNKNOWN_OBJECT) {
          /* look for non-whitespace */
          for ($i = 0;(($i < $len) && (preg_match("/ |\n|\t/", $s[$i])));$i++);
          $i++;
          /* if we found non-whitespace, this is a literal */
          if ($i <= $len) {
            $this->rdf_parser["top"]["state"] = self::IN_PROPERTY_LITERAL;
          }
        }

        break;
      case self::IN_TOP_LEVEL:
      case self::IN_PROPERTY_PARSE_TYPE_LITERAL:
      case self::IN_XML:
        $this->_report_character_data($s, strlen($s));
        break;
      case self::IN_RDF:
      case self::IN_DESCRIPTION:
      case self::IN_PROPERTY_RESOURCE:
      case self::IN_PROPERTY_EMPTY_RESOURCE:
      case self::IN_PROPERTY_PARSE_TYPE_RESOURCE:
      case self::IN_UNKNOWN:
        break;
    }
  }
}

?>