GraphViz.php

<?php

/**
 * EasyRdf
 *
 * LICENSE
 *
 * Copyright (c) 2012 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) 2009-2012 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 * @version    $Id$
 */

/**
 * Class to serialise an EasyRdf_Graph to GraphViz
 *
 * Depends upon the GraphViz 'dot' command line tools to render images.
 *
 * See http://www.graphviz.org/ for more information.
 *
 * @package    EasyRdf
 * @copyright  Copyright (c) 2012 Nicholas J Humfrey
 * @license    http://www.opensource.org/licenses/bsd-license.php
 */
class EasyRdf_Serialiser_GraphViz extends EasyRdf_Serialiser {
  private $dotCommand = 'dot';
  private $useLabels = false;
  private $onlyLabelled = false;
  private $attributes = array(
    'charset' => 'utf-8',
  );

  /**
   * Constructor
   *
   * @return object EasyRdf_Serialiser_GraphViz
   */
  public function __construct() {
  }

  /**
   * Set the path to the GraphViz 'dot' command
   *
   * Default is to search PATH for the command 'dot'.
   *
   * @param string $cmd   The path to the 'dot' command.
   * @return object EasyRdf_Serialiser_GraphViz
   */
  public function setDotCommand($cmd) {
    $this->dotCommand = $cmd;
    return $this;
  }

  /**
   * Get the path to the GraphViz 'dot' command
   *
   * The default value is simply 'dot'
   *
   * @return string The path to the 'dot' command.
   */
  public function getDotCommand() {
    return $this->dotCommand;
  }

  /**
   * Turn on/off the option to display labels instead of URIs.
   *
   * When this option is turned on, then labels for resources will
   * be displayed instead of the full URI of a resource. This makes
   * it simpler to create friendly diagrams that non-technical people
   * can understand.
   *
   * This option is turned off by default.
   *
   * @param bool $useLabels   A boolean value to turn labels on and off
   * @return object EasyRdf_Serialiser_GraphViz
   */
  public function setUseLabels($useLabels) {
    $this->useLabels = $useLabels;
    return $this;
  }

  /**
   * Get the state of the use labels option
   *
   * @return bool The current state of the use labels option
   */
  public function getUseLabels() {
    return $this->useLabels;
  }

  /**
   * Turn on/off the option to only display nodes and edges with labels
   *
   * When this option is turned on, then only nodes (resources and literals)
   * and edges (properties) will only be displayed if they have a label. You
   * can use this option, to create concise, diagrams of your data, rather than
   * the RDF.
   *
   * This option is turned off by default.
   *
   * @param bool $onlyLabelled   A boolean value to enable/display only labelled items
   * @return object EasyRdf_Serialiser_GraphViz
   */
  public function setOnlyLabelled($onlyLabelled) {
    $this->onlyLabelled = $onlyLabelled;
    return $this;
  }

  /**
   * Get the state of the only Only Labelled option
   *
   * @return bool The current state of the Only Labelled option
   */
  public function getOnlyLabelled() {
    return $this->onlyLabelled;
  }

  /**
   * Set an attribute on the GraphViz graph
   *
   * Example:
   *     $serialiser->setAttribute('rotate', 90);
   *
   * See the GraphViz tool documentation for information about the
   * available attributes.
   *
   * @param string $name    The name of the attribute
   * @param string $value   The value for the attribute
   * @return object EasyRdf_Serialiser_GraphViz
   */
  public function setAttribute($name, $value) {
    $this->attributes[$name] = $value;
    return $this;
  }

  /**
   * Get an attribute of the GraphViz graph
   *
   * @param string $name    Attribute name
   * @return string The value of the graph attribute
   */
  public function getAttribute($name) {
    return $this->attributes[$name];
  }

  /**
   * Convert an EasyRdf object into a GraphViz node identifier
   *
   * @ignore
   */
  protected function nodeName($entity) {
    if ($entity instanceof EasyRdf_Resource) {
      if ($entity
        ->isBnode()) {
        return "B" . $entity
          ->getUri();
      }
      else {
        return "R" . $entity
          ->getUri();
      }
    }
    else {
      return "L" . $entity;
    }
  }

  /**
   * Internal function to escape a string into DOT safe syntax
   *
   * @ignore
   */
  protected function escape($input) {
    if (preg_match('/^([a-z_][a-z_0-9]*|-?(\\.[0-9]+|[0-9]+(\\.[0-9]*)?))$/i', $input)) {
      return $input;
    }
    else {
      return '"' . str_replace(array(
        "\r\n",
        "\n",
        "\r",
        '"',
      ), array(
        '\\n',
        '\\n',
        '\\n',
        '\\"',
      ), $input) . '"';
    }
  }

  /**
   * Internal function to escape an associate array of attributes and
   * turns it into a DOT notation string
   *
   * @ignore
   */
  protected function escapeAttributes($array) {
    $items = '';
    foreach ($array as $k => $v) {
      $items[] = $this
        ->escape($k) . '=' . $this
        ->escape($v);
    }
    return '[' . implode(',', $items) . ']';
  }

  /**
   * Internal function to create dot syntax line for either a node or an edge
   *
   * @ignore
   */
  protected function serialiseRow($node1, $node2 = null, $attributes = array()) {
    $result = '  ' . $this
      ->escape($node1);
    if ($node2) {
      $result .= ' -> ' . $this
        ->escape($node2);
    }
    if (count($attributes)) {
      $result .= ' ' . $this
        ->escapeAttributes($attributes);
    }
    return $result . ";\n";
  }

  /**
   * Internal function to serialise an EasyRdf_Graph into a DOT formatted string
   *
   * @ignore
   */
  protected function serialiseDot($graph) {
    $result = "digraph {\n";

    // Write the graph attributes
    foreach ($this->attributes as $k => $v) {
      $result .= '  ' . $this
        ->escape($k) . '=' . $this
        ->escape($v) . ";\n";
    }

    // Go through each of the properties and write the edges
    $nodes = array();
    $result .= "\n  // Edges\n";
    foreach ($graph
      ->resources() as $resource) {
      $name1 = $this
        ->nodeName($resource);
      foreach ($resource
        ->propertyUris() as $property) {
        $label = null;
        if ($this->useLabels) {
          $label = $graph
            ->resource($property)
            ->label();
        }
        if ($label === null) {
          if ($this->onlyLabelled == true) {
            continue;
          }
          else {
            $label = EasyRdf_Namespace::shorten($property);
          }
        }
        foreach ($resource
          ->all("<{$property}>") as $value) {
          $name2 = $this
            ->nodeName($value);
          $nodes[$name1] = $resource;
          $nodes[$name2] = $value;
          $result .= $this
            ->serialiseRow($name1, $name2, array(
            'label' => $label,
          ));
        }
      }
    }
    ksort($nodes);
    $result .= "\n  // Nodes\n";
    foreach ($nodes as $name => $node) {
      $type = substr($name, 0, 1);
      $label = '';
      if ($type == 'R') {
        if ($this->useLabels) {
          $label = $node
            ->label();
        }
        if (!$label) {
          $label = $node
            ->shorten();
        }
        if (!$label) {
          $label = $node
            ->getURI();
        }
        $result .= $this
          ->serialiseRow($name, null, array(
          'URL' => $node
            ->getURI(),
          'label' => $label,
          'shape' => 'ellipse',
          'color' => 'blue',
        ));
      }
      elseif ($type == 'B') {
        if ($this->useLabels) {
          $label = $node
            ->label();
        }
        $result .= $this
          ->serialiseRow($name, null, array(
          'label' => $label,
          'shape' => 'circle',
          'color' => 'green',
        ));
      }
      else {
        $result .= $this
          ->serialiseRow($name, null, array(
          'label' => strval($node),
          'shape' => 'record',
        ));
      }
    }
    $result .= "}\n";
    return $result;
  }

  /**
   * Internal function to render a graph into an image
   *
   * @ignore
   */
  public function renderImage($graph, $format = 'png') {
    $dot = $this
      ->serialiseDot($graph);
    return EasyRdf_Utils::execCommandPipe($this->dotCommand, array(
      "-T{$format}",
    ), $dot);
  }

  /**
   * Serialise an EasyRdf_Graph into a GraphViz dot document.
   *
   * Supported output format names: dot, gif, png, svg
   *
   * @param string $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, $format);
    switch ($format) {
      case 'dot':
        return $this
          ->serialiseDot($graph);
      case 'png':
      case 'gif':
      case 'svg':
        return $this
          ->renderImage($graph, $format);
      default:
        throw new EasyRdf_Exception("EasyRdf_Serialiser_GraphViz does not support: {$format}");
    }
  }

}