<?php rcs_id('$Id: SemanticWeb.php,v 1.3 2007-01-03 21:25:21 rurban Exp $');
/**
 * What to do on ?format=rdf  What to do on ?format=owl
 *
 * Map relations on a wikipage to a RDF ressource to build a "Semantic Web" 
 * - a web ontology frontend compatible to OWL (web ontology language).
 * http://www.w3.org/2001/sw/Activity
 * Simple RDF ontologies contain facts and rules, expressed by RDF triples:
 *   Subject (page) -> Predicate (verb, relation) -> Object (links)
 * OWL extents that to represent a typical OO framework. 
 *  OO predicates: 
 *    is_a, has_a, ...
 *  OWL predicates:
 *    subClassOf, restrictedBy, onProperty, intersectionOf, allValuesFrom, ...
 *    someValuesFrom, unionOf, equivalentClass, disjointWith, ...
 *    plus the custom vocabulary (ontology): canRun, canBite, smellsGood, ...
 *  OWL Subjects: Class, Restriction, ...
 *  OWL Properties: type, label, comment, ...
 * DAML should also be supported.
 *
 * Purpose:
 * - Another way to represent various KB models in various DL languages. 
 *   (OWL/DAML/other DL)
 * - Frontend to various KB model reasoners and representations. 
 * - Generation/update of static wiki pages based on external OWL/DL/KB 
 *   (=> ModelTest/Categories)
 *   KB Blackboard and Visualization.
 * - OWL generation based on static wiki pages (ModelTest?format=owl)
 *
 * Facts: (may be represented by special links on a page)
 *  - Each page must be representable with an unique URL.
 *  - Each fact must be representable with an unique RDF triple.
 *  - A class is represented by a category page.
 *  - To represent more expressive description logic, "enriched" 
 *    links will not be enough (? variable symbolic objects).
 *
 * Rules: (may be represented by special content on a page)
 *  - Syntax: reasoner backend specific, or common or ?
 *
 * RDF Triple: (representing facts)
 *   Subject (page) -> Predicate (verb, relation) -> Object (links)
 * Subject: a page
 * Verb: 
 *   Special link qualifiers represent RDF triples, based on RDF standard notation.
 *   See RDF standard DTD's on daml.org and w3.org, plus your custom predicates. 
 *   (need your own DTD)
 *   Example: page [Ape] isa:Animal, ...
 * Object: special links on a page.
 * Class: WikiCategory
 * Model: Basepage for a KB. (parametrizeable pages or copies of modified snapshots?)
 *
 * DL: Description Logic
 * KB: Knowledge Base
 *
 * Discussion:
 * Of course *real* expert systems ("reasoners") will help/must be used in
 * optimization and maintainance of the SemanticWeb KB (Knowledge
 * Base). Hooks will be tested to KM (an interactive KB playground),
 * LISA (standard unifier), FaCT, RACER, ... 

 * Maybe also ZEBU (parser generator) is needed to convert the wiki KB
 * syntax to the KB reasoner backend (LISA, KM, CLIPS, JESS, FaCT,
 * ...) and forth.

 * pOWL is a simple php backend with some very simple AI logic in PHP,
 * though I strongly doubt the usefulness of reasoners not written in
 * Common Lisp.
 *
 * SEAL (omntoweb.org) is similar to that, just on top of the Zope CMF.
 * FaCT uses e.g. this KB DTD:
<!ELEMENT KNOWLEDGEBASE (DEFCONCEPT|DEFROLE|IMPLIESC|EQUALC|IMPLIESR|EQUALR|TRANSITIVE|FUNCTIONAL)*> 
<!ELEMENT CONCEPT (PRIMITIVE|TOP|BOTTOM|AND|OR|NOT|SOME|ALL|ATMOST|ATLEAST)> 
<!ELEMENT ROLE (PRIMROLE|INVROLE)> 
... (facts and rules described in XML)
 *
 * Links:
 *   http://phpwiki.org/SemanticWeb, 
 *   http://en.wikipedia.org/wiki/Knowledge_representation
 *   http://www.ontoweb.org/
 *   http://www.semwebcentral.org/ (OWL on top of GForge)
 *
 *
 * Author: Reini Urban <rurban@x-ray.at>
 */
/*============================================================================*/
/*
 Copyright 2004,2007 Reini Urban

 This file is part of PhpWiki.

 PhpWiki is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2 of the License, or
 (at your option) any later version.

 PhpWiki is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with PhpWiki; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

include_once('lib/RssWriter.php');
include_once('lib/Units.php');
include_once("lib/TextSearchQuery.lib");

/**
 * RdfWriter - A class to represent a wikipage as RDF. Supports ?format=rdf
 *
 * RdfWriter
 *  - RssWriter
 *    - RecentChanges (RecentChanges?format=rss)
 *      channel: ... item: ...
 */
class RdfWriter extends RssWriter // in fact it should be rewritten to be other way round.
{
    function RdfWriter () {
        $this->XmlElement('rdf:RDF',
                          array('xmlns' => "http://purl.org/rss/1.0/",
                                'xmlns:rdf' => 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'));

	$this->_modules = array(
            //Standards
	    'content'	=> "http://purl.org/rss/1.0/modules/content/",
	    'dc'	=> "http://purl.org/dc/elements/1.1/",
	    );

	$this->_uris_seen = array();
        $this->_items = array();
    }
}

/**
 * OwlWriter - A class to represent a set of wiki pages (a DL model) as OWL. 
 * Supports ?format=owl
 *
 * OwlWriter
 *  - RdfWriter
 *  - Reasoner
*/
class OwlWriter extends RdfWriter {
};

/**
 * ModelWriter - Export a KB as set of wiki pages. 
 * Probably based on some convenient DL expression syntax. (deffact, defrule, ...)
 *
 * ModelWriter
 *  - OwlWriter
 *  - ReasonerBackend
*/
class ModelWriter extends OwlWriter {
};

/**
 *  NumericSearchQuery can do: 
 *         ("population < 20000 and area > 1000000", array("population", "area"))
 *  ->match(array('population' => 100000, 'area' => 10000000)) 
 * @see NumericSearchQuery
 *
 *  SemanticAttributeSearchQuery can detect and unify units in numbers.
 *         ("population < 2million and area > 100km2", array("population", "area"))
 *  ->match(array('population' => 100000, 'area' => 10000000))
 *
 * Do we need a real parser or can we just regexp over some allowed unit 
 * suffixes to detect the numbers?
 * see man units(1) and /usr/share/units.dat
 * base units: $ units "1 million miles"
 *                     Definition: 1.609344e+09 m
 */
class SemanticAttributeSearchQuery
extends NumericSearchQuery
{
    /*
    var $base_units = array('m'   => explode(',','km,miles,cm,dm,mm,ft,inch,inches,meter'),
			    'm^2' => explode(',','km^2,ha,cm^2,mi^2'),
			    'm^3' => explode(',','km^3,lit,cm^3,dm^3,gallons'),
			    );
    */

    /**
     * We need to detect units from the freetext query:
     * population > 1 million
     */
    function SemanticAttributeSearchQuery($search_query, $placeholders, $unit = '') {
	$this->NumericSearchQuery($search_query, $placeholders);
	$this->_units = new Units();
	$this->unit = $unit;
    }

    /**
     * Strip non-numeric chars from the variable (as the groupseperator) and replace 
     * it in the symbolic query for evaluation.
     * This version unifies the attribute values from the database to a 
     * numeric basevalue before comparison. (area:=963.6km^2 => 9.366e+08 m^2)
     *
     * @access private
     * @param $value number   A numerical value: integer, float or string.
     * @param $x string       The variable name to be replaced in the query.
     * @return string
     */
    function _bind($value, $x) {
    	$ori_value = $value;
	$value = preg_replace("/,/", "", $value);
	$this->_bound[] = array('linkname'  => $x,
	        		'linkvalue' => $value);
	// We must ensure that the same baseunits are matched against. 
	// We cannot compare m^2 to m or ''
	$val_base = $this->_units->basevalue($value);
        if (!DISABLE_UNITS and $this->_units->baseunit($value) != $this->unit) {
	    // Poor user has selected an attribute, but no unit. assume he means the baseunit
	    if (count($this->getVars() == 1) and $this->unit == '') {
		;
	    } else {
		// non-matching units are silently ignored
		$this->_workquery = '';
		return '';
	    }
        }
        $value = $val_base;
	if (!is_numeric($value)) {
	    $this->_workquery = ''; //must return false
	    trigger_error("Cannot match against non-numeric attribute value $x := $ori_value", 
			  E_USER_NOTICE);
	    return '';
	}

	$this->_workquery = preg_replace("/\b".preg_quote($x,"/")."\b/", $value, $this->_workquery);
	return $this->_workquery;
    }

}

/**
 *  SemanticSearchQuery can do:
 *     (is_a::city and population < 20000) and (*::city and area > 1000000)
 *  ->match(array('is_a' => 'city', 'linkfrom' => array(), 
 *          population' => 100000, 'area' => 10000000))
 * @return array  A list of found and bound matches
 */
class SemanticSearchQuery
extends SemanticAttributeSearchQuery
{
    function hasAttributes() { // TODO 
    }
    function hasRelations()  { // TODO 
    }
    function getLinkNames()  { // TODO 
    }
}

/**
 * ReasonerBackend - hooks to reasoner backends.
 * via http as with DIG,
 * or internally
 */
class ReasonerBackend {
    function ReasonerBackend () {
        ;
    }
    /**
     * transform to reasoner syntax
     */
    function transformTo () {
        ;
    }
    /**
     * transform from reasoner syntax
     */
    function transformFrom () {
        ;
    }
    /**
     * call the reasoner
     */
    function invoke () {
        ;
    }
};

class ReasonerBackend_LISA extends ReasonerBackend {
};

class ReasonerBackend_KM extends ReasonerBackend {
};


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?>