class EasyRdf_Serialiser_RdfXml

Format.php in drupal/core/vendor/easyrdf/easyrdf/lib/EasyRdf/Format.php

class EasyRdf_Serialiser_RdfXml extends EasyRdf_Serialiser {
  private $outputtedResources = array();

  /** A constant for the RDF Type property URI */
  const RDF_XML_LITERAL = 'http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral';

  /**
   * Protected method to serialise an object node into an XML object
   * @ignore
   */
  protected function rdfxmlObject($property, $obj, $depth) {
    $indent = str_repeat('  ', $depth);
    if (is_object($obj) and $obj instanceof EasyRdf_Resource) {
      $pcount = count($obj
        ->propertyUris());
      $rpcount = $this
        ->reversePropertyCount($obj);
      $alreadyOutput = isset($this->outputtedResources[$obj
        ->getUri()]);
      $tag = "{$indent}<{$property}";
      if ($obj
        ->isBNode()) {
        if ($alreadyOutput or $rpcount > 1 or $pcount == 0) {
          $tag .= " rdf:nodeID=\"" . htmlspecialchars($obj
            ->getNodeId()) . '"';
        }
      }
      else {
        if ($alreadyOutput or $rpcount != 1 or $pcount == 0) {
          $tag .= " rdf:resource=\"" . htmlspecialchars($obj
            ->getURI()) . '"';
        }
      }
      if ($alreadyOutput == false and $rpcount == 1 and $pcount > 0) {
        $xml = $this
          ->rdfxmlResource($obj, false, $depth + 1);
        if ($xml) {
          return "{$tag}>{$xml}{$indent}</{$property}>\n\n";
        }
        else {
          return '';
        }
      }
      else {
        return $tag . "/>\n";
      }
    }
    elseif (is_object($obj) and $obj instanceof EasyRdf_Literal) {
      $atrributes = "";
      $datatype = $obj
        ->getDatatypeUri();
      if ($datatype) {
        if ($datatype == self::RDF_XML_LITERAL) {
          $atrributes .= " rdf:parseType=\"Literal\"";
          $value = strval($obj);
        }
        else {
          $datatype = htmlspecialchars($datatype);
          $atrributes .= " rdf:datatype=\"{$datatype}\"";
        }
      }
      elseif ($obj
        ->getLang()) {
        $atrributes .= ' xml:lang="' . htmlspecialchars($obj
          ->getLang()) . '"';
      }

      // Escape the value
      if (!isset($value)) {
        $value = htmlspecialchars(strval($obj));
      }
      return "{$indent}<{$property}{$atrributes}>{$value}</{$property}>\n";
    }
    else {
      throw new EasyRdf_Exception("Unable to serialise object to xml: " . getType($obj));
    }
  }

  /**
   * Protected method to serialise a whole resource and its properties
   * @ignore
   */
  protected function rdfxmlResource($res, $showNodeId, $depth = 1) {

    // Keep track of the resources we have already serialised
    if (isset($this->outputtedResources[$res
      ->getUri()])) {
      return '';
    }
    else {
      $this->outputtedResources[$res
        ->getUri()] = true;
    }

    // If the resource has no properties - don't serialise it
    $properties = $res
      ->propertyUris();
    if (count($properties) == 0) {
      return '';
    }
    $type = $res
      ->type();
    if ($type) {
      $this
        ->addPrefix($type);
    }
    else {
      $type = 'rdf:Description';
    }
    $indent = str_repeat('  ', $depth);
    $xml = "\n{$indent}<{$type}";
    if ($res
      ->isBNode()) {
      if ($showNodeId) {
        $xml .= ' rdf:nodeID="' . htmlspecialchars($res
          ->getNodeId()) . '"';
      }
    }
    else {
      $xml .= ' rdf:about="' . htmlspecialchars($res
        ->getUri()) . '"';
    }
    $xml .= ">\n";
    foreach ($properties as $property) {
      $short = EasyRdf_Namespace::shorten($property, true);
      if ($short) {
        $this
          ->addPrefix($short);
        $objects = $res
          ->all("<{$property}>");
        if ($short == 'rdf:type') {
          array_shift($objects);
        }
        foreach ($objects as $object) {
          $xml .= $this
            ->rdfxmlObject($short, $object, $depth + 1);
        }
      }
      else {
        throw new EasyRdf_Exception("It is not possible to serialse the property " . "'{$property}' to RDF/XML.");
      }
    }
    $xml .= "{$indent}</{$type}>\n";
    return $xml;
  }

  /**
   * Method to serialise an EasyRdf_Graph to RDF/XML
   *
   * @param object EasyRdf_Graph $graph   An EasyRdf_Graph object.
   * @param string  $format               The name of the format to convert to.
   * @return string                       The RDF in the new desired format.
   */
  public function serialise($graph, $format) {
    parent::checkSerialiseParams($graph, $format);
    if ($format != 'rdfxml') {
      throw new EasyRdf_Exception("EasyRdf_Serialiser_RdfXml does not support: {$format}");
    }

    // store of namespaces to be appended to the rdf:RDF tag
    $this->prefixes = array(
      'rdf' => true,
    );

    // store of the resource URIs we have serialised
    $this->outputtedResources = array();
    $xml = '';
    foreach ($graph
      ->resources() as $resource) {
      $xml .= $this
        ->rdfxmlResource($resource, true, 1);
    }

    // iterate through namepsaces array prefix and output a string.
    $namespaceStr = '';
    foreach ($this->prefixes as $prefix => $count) {
      $url = EasyRdf_Namespace::get($prefix);
      if (strlen($namespaceStr)) {
        $namespaceStr .= "\n        ";
      }
      $namespaceStr .= ' xmlns:' . $prefix . '="' . htmlspecialchars($url) . '"';
    }
    return "<?xml version=\"1.0\" encoding=\"utf-8\" ?>\n" . "<rdf:RDF" . $namespaceStr . ">\n" . $xml . "\n</rdf:RDF>\n";
  }

}