Serialiser.php

<?php

/**
 * EasyRdf
 *
 * LICENSE
 *
 * Copyright (c) 2009-2010 Nicholas J Humfrey.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author 'Nicholas J Humfrey" may be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2010 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 * @version    $Id$
 */

/**
 * Parent class for the EasyRdf serialiser
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2009-2010 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 */
class EasyRdf_Serialiser {
  protected $prefixes = array();

  /**
   * Keep track of the prefixes used while serialising
   * @ignore
   */
  protected function addPrefix($qname) {
    list($prefix) = explode(':', $qname);
    $this->prefixes[$prefix] = true;
  }

  /**
   * Check and cleanup parameters passed to serialise() method
   * @ignore
   */
  protected function checkSerialiseParams(&$graph, &$format) {
    if ($graph == null or !is_object($graph) or get_class($graph) != 'EasyRdf_Graph') {
      throw new InvalidArgumentException("\$graph should be an EasyRdf_Graph object and cannot be null");
    }
    if ($format == null or $format == '') {
      throw new InvalidArgumentException("\$format cannot be null or empty");
    }
    elseif (is_object($format) and get_class($format) == 'EasyRdf_Format') {
      $format = $format
        ->getName();
    }
    elseif (!is_string($format)) {
      throw new InvalidArgumentException("\$format should be a string or an EasyRdf_Format object");
    }
  }

  /**
   * Protected method to get the number of reverse properties for a resource
   * If a resource only has a single property, the number of values for that
   * property is returned instead.
   * @ignore
   */
  protected function reversePropertyCount($resource) {
    $properties = $resource
      ->reversePropertyUris();
    $count = count($properties);
    if ($count == 1) {
      $property = $properties[0];
      return $resource
        ->count("^<{$property}>");
    }
    else {
      return $count;
    }
  }

  /**
   * Sub-classes must follow this protocol
   * @ignore
   */
  public function serialise($graph, $format) {
    throw new EasyRdf_Exception("This method should be overridden by sub-classes.");
  }

}