| 1 | <?php
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| 2 | // ----------------------------------------------------------------------------------
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| 3 | // Class: InfRule
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| 4 | // ----------------------------------------------------------------------------------
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| 5 |
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| 6 | /**
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| 7 | * This class represents a single rule in a RDFS inference model.
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| 8 | * It primary constists of a trigger and an entailment.
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| 9 | * In the forward-chaining mode (RDFSFModel) a statement is checked,
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| 10 | * if it satisfies the trigger. If it does, a new statement is returned.
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| 11 | * In the backward-chaining mode (RDFSBModel) a find-query is checked
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| 12 | * with the entailment. If this entailment could satify the find-query,
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| 13 | * a new find-query is returned, that searches for statements that
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| 14 | * satisfy the trigger of this rule.
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| 15 | *
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| 16 | * @version $Id: InfRule.php 290 2006-06-22 12:23:24Z tgauss $
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| 17 | * @author Daniel Westphal <mail at d-westphal dot de>
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| 18 |
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| 19 | *
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| 20 | * @package infModel
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| 21 | * @access public
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| 22 | **/
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| 23 |
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| 24 | class InfRule
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| 25 | {
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| 26 |
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| 27 | /**
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| 28 | * Array, that hold the trigger subject in key ['s'], the trigger
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| 29 | * predicate in ['p'], and the trigger object in ['o'].
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| 30 | * The array values can be NULL to match anything or be a node that
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| 31 | * has to be matched.
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| 32 | *
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| 33 | * @var array
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| 34 | * @access private
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| 35 | */
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| 36 | var $trigger;
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| 37 |
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| 38 | /**
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| 39 | * Array, that hold the entailment subject in key ['s'], the
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| 40 | * entailment predicate in ['p'], and the entailment object in ['o'].
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| 41 | * The array values can be a node that will be inserted in the
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| 42 | * returning statement, or '<s>' to insert the subject,'<p>' to insert
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| 43 | * the predicate, or '<o>' to insert the object of the checked statement
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| 44 | * to this position in the new returned statement.
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| 45 | *
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| 46 | * @var array
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| 47 | * @access private
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| 48 | */
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| 49 | var $entailment;
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| 50 |
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| 51 |
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| 52 | /**
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| 53 | * Constructor
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| 54 | *
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| 55 | *
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| 56 | * @access public
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| 57 | */
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| 58 | function infRule()
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| 59 | {
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| 60 | //initialising vars
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| 61 | $this->trigger=array();
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| 62 | $this->entailment=array();
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| 63 | }
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| 64 |
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| 65 | /**
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| 66 | * Sets the trigger of this rule
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| 67 | * The values can be NULL to match anything or be a node that has to
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| 68 | * be matched.
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| 69 | *
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| 70 | * @param object Node OR NULL $subject
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| 71 | * @param object Node OR NULL $predicate
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| 72 | * @param object Node OR NULL $object
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| 73 | * @access public
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| 74 | * @throws PhpError
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| 75 | */
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| 76 | function setTrigger ($subject, $predicate, $object)
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| 77 | {
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| 78 | //throw an error if subject, predicate, or object are neither
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| 79 | //node, nor null.
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| 80 | if(!is_a($subject,'Node') && $subject != null)
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| 81 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 82 | setTrigger): $subject has to be null or of class Node'
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| 83 | , E_USER_ERROR);
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| 84 | if(!is_a($predicate,'Node') && $predicate != null)
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| 85 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 86 | setTrigger): $predicate has to be null or of class Node'
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| 87 | , E_USER_ERROR);
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| 88 | if(!is_a($object,'Node') && $object != null)
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| 89 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 90 | setTrigger): $object has to be null or of class Node'
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| 91 | , E_USER_ERROR);
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| 92 |
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| 93 | //set the trigger
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| 94 | $this->trigger['s']=$subject;
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| 95 | $this->trigger['p']=$predicate;
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| 96 | $this->trigger['o']=$object;
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| 97 | }
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| 98 |
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| 99 | /**
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| 100 | * Sets the entailment of this rule
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| 101 | * The values can be NULL to match anything or be a node that has to
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| 102 | * be matched.
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| 103 | *
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| 104 | * @param object Node OR NULL $subject
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| 105 | * @param object Node OR NULL $predicate
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| 106 | * @param object Node OR NULL $object
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| 107 | * @access public
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| 108 | * @throws PhpError
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| 109 | */
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| 110 | function setEntailment($subject,$predicate,$object)
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| 111 | {
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| 112 | //throw an error if subject, predicate, or object are neither node,
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| 113 | //nor <s>,<p>,<o>.
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| 114 | if(!is_a($subject,'Node') && !ereg('<[spo]>', $subject))
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| 115 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 116 | setEntailment): $subject has to be <s>,<p>,or <o> or of class Node'
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| 117 | , E_USER_ERROR);
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| 118 | if(!is_a($predicate,'Node') && !ereg('<[spo]>', $predicate))
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| 119 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 120 | setEntailment): $predicate has to be <s>,<p>,or <o> or of class Node'
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| 121 | , E_USER_ERROR);
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| 122 | if(!is_a($object,'Node') && !ereg('<[spo]>', $object))
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| 123 | trigger_error(RDFAPI_ERROR . '(class: Infrule; method:
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| 124 | setEntailment): $object has to be <s>,<p>,or <o> or of class Node'
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| 125 | , E_USER_ERROR);
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| 126 |
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| 127 | $this->entailment['s']=$subject;
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| 128 | $this->entailment['p']=$predicate;
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| 129 | $this->entailment['o']=$object;
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| 130 | }
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| 131 |
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| 132 | /**
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| 133 | * Checks, if the statement satisfies the trigger.
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| 134 | *
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| 135 | * @param object Statement
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| 136 | * @return boolean
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| 137 | * @access public
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| 138 | * @throws PhpError
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| 139 | */
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| 140 | function checkTrigger(& $statement)
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| 141 | {
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| 142 | //is true, if the trigger is null to match anything
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| 143 | //or equals the statement's subject
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| 144 | $shouldFireS = $this->trigger['s'] == null ||
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| 145 | $this->trigger['s']->equals($statement->getSubject());
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| 146 |
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| 147 | //is true, if the trigger is null to match anything
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| 148 | //or equals the statement's predicate
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| 149 | $shouldFireP = $this->trigger['p'] == null ||
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| 150 | $this->trigger['p']->equals($statement->getPredicate());
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| 151 |
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| 152 | //is true, if the trigger is null to match anything
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| 153 | //or equals the statement's object
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| 154 | $shouldFireO = $this->trigger['o'] == null ||
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| 155 | $this->trigger['o']->equals($statement->getObject());
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| 156 |
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| 157 | //returns true, if ALL are true
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| 158 | return $shouldFireS && $shouldFireP && $shouldFireO;
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| 159 | }
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| 160 |
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| 161 | /**
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| 162 | * Checks, if this rule could entail a statement that matches
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| 163 | * a find of $subject,$predicate,$object.
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| 164 | *
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| 165 | * @param object Statement
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| 166 | * @return boolean
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| 167 | * @access public
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| 168 | * @throws PhpError
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| 169 | */
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| 170 | function checkEntailment ($subject, $predicate, $object)
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| 171 | {
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| 172 | //true, if $subject is null, the entailment's subject matches
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| 173 | //anything, or the $subject equals the entailment-subject.
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| 174 | $matchesS= $subject == null ||
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| 175 | !is_a($this->entailment['s'],'Node') ||
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| 176 | $this->entailment['s']->equals($subject);
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| 177 |
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| 178 | //true, if $predicate is null, the entailment's predicate matches
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| 179 | //anything, or the $predicate equals the entailment-predicate.
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| 180 | $matchesP= $predicate == null ||
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| 181 | !is_a($this->entailment['p'],'Node') ||
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| 182 | $this->entailment['p']->equals($predicate);
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| 183 |
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| 184 | //true, if $object is null, the entailment's object matches
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| 185 | //anything, or the $object equals the entailment-object.
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| 186 | $matchesO= $object == null ||
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| 187 | !is_a($this->entailment['o'],'Node') ||
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| 188 | $this->entailment['o']->equals($object);
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| 189 |
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| 190 | //returns true, if ALL are true
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| 191 | return $matchesS && $matchesP && $matchesO;
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| 192 | }
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| 193 |
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| 194 | /**
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| 195 | * Returns a infered InfStatement by evaluating the statement with
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| 196 | * the entailment rule.
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| 197 | *
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| 198 | * @param object Statement
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| 199 | * @return object InfStatement
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| 200 | * @access public
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| 201 | * @throws PhpError
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| 202 | */
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| 203 | function entail(& $statement)
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| 204 | {
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| 205 | //if the entailment's subject is <s>,<p>,or <o>, put the statements
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| 206 | //subject,predicate,or object into the subject of the
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| 207 | //entailed statement. If the entailment's subject is a node,
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| 208 | //add that node to the statement.
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| 209 | switch ($this->entailment['s'])
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| 210 | {
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| 211 | case '<s>':
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| 212 | $entailedSubject=$statement->getSubject();
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| 213 | break;
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| 214 | case '<p>':
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| 215 | $entailedSubject=$statement->getPredicate();
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| 216 | break;
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| 217 | case '<o>':
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| 218 | $entailedSubject=$statement->getObject();
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| 219 | break;
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| 220 | default:
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| 221 | $entailedSubject=$this->entailment['s'];
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| 222 | };
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| 223 |
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| 224 | //if the entailment's predicate is <s>,<p>,or <o>, put the
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| 225 | //statements subject,predicate,or object into the predicate of
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| 226 | //the entailed statement. If the entailment's predicate is a node,
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| 227 | //add that node to the statement.
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| 228 | switch ($this->entailment['p'])
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| 229 | {
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| 230 | case '<s>':
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| 231 | $entailedPredicate=$statement->getSubject();
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| 232 | break;
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| 233 | case '<p>':
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| 234 | $entailedPredicate=$statement->getPredicate();
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| 235 | break;
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| 236 | case '<o>':
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| 237 | $entailedPredicate=$statement->getObject();
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| 238 | break;
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| 239 | default:
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| 240 | $entailedPredicate=$this->entailment['p'];
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| 241 | };
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| 242 |
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| 243 | //if the entailment's object is <s>,<p>,or <o>, put the
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| 244 | //statements subject,predicate,or object into the object of
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| 245 | //the entailed statement. If the entailment's object is a node,
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| 246 | //add that node to the statement.
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| 247 | switch ($this->entailment['o'])
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| 248 | {
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| 249 | case '<s>':
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| 250 | $entailedObject=$statement->getSubject();
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| 251 | break;
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| 252 | case '<p>':
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| 253 | $entailedObject=$statement->getPredicate();
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| 254 | break;
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| 255 | case '<o>':
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| 256 | $entailedObject=$statement->getObject();
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| 257 | break;
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| 258 | default:
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| 259 | $entailedObject=$this->entailment['o'];
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| 260 | };
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| 261 |
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| 262 | //return the infered statement
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| 263 | return (new InfStatement($entailedSubject,$entailedPredicate,$entailedObject));
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| 264 | }
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| 265 |
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| 266 | /**
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| 267 | * Returns a find-query that matches statements, whose entailed
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| 268 | * statements would match the supplied find query.
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| 269 | *
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| 270 | * @param Node OR null $subject
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| 271 | * @param Node OR null $predicate
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| 272 | * @param Node OR null $object
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| 273 | * @return array
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| 274 | * @access public
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| 275 | * @throws PhpError
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| 276 | */
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| 277 | function getModifiedFind( $subject, $predicate, $object)
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| 278 | {
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| 279 | $findSubject=$this->trigger['s'];
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| 280 | $findPredicate=$this->trigger['p'];
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| 281 | $findObject=$this->trigger['o'];
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| 282 |
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| 283 | switch ($this->entailment['s'])
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| 284 | {
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| 285 | case '<s>':
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| 286 | $findSubject=$subject;
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| 287 | break;
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| 288 | case '<p>':
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| 289 | $findPredicate=$subject;
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| 290 | break;
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| 291 | case '<o>':
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| 292 | $findObject=$subject;
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| 293 | break;
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| 294 | };
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| 295 |
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| 296 | switch ($this->entailment['p'])
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| 297 | {
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| 298 | case '<s>':
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| 299 | $findSubject=$predicate;
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| 300 | break;
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| 301 | case '<p>':
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| 302 | $findPredicate=$predicate;
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| 303 | break;
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| 304 | case '<o>':
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| 305 | $findObject=$predicate;
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| 306 | break;
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| 307 | };
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| 308 |
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| 309 | switch ($this->entailment['o'])
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| 310 | {
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| 311 | case '<s>':
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| 312 | $findSubject=$object;
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| 313 | break;
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| 314 | case '<p>':
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| 315 | $findPredicate=$object;
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| 316 | break;
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| 317 | case '<o>':
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| 318 | $findObject=$object;
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| 319 | break;
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| 320 | };
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| 321 |
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| 322 | return array('s' => $findSubject,
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| 323 | 'p' => $findPredicate,
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| 324 | 'o' => $findObject );
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| 325 | }
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| 326 |
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| 327 | function getTrigger()
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| 328 | {
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| 329 | return array ( 's' => $this->trigger['s'],
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| 330 | 'p' => $this->trigger['p'],
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| 331 | 'o' => $this->trigger['o'],
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| 332 | );
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| 333 | }
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| 334 |
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| 335 | function getEntailment()
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| 336 | {
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| 337 | return array ( 's' => $this->entailment['s'],
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| 338 | 'p' => $this->entailment['p'],
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| 339 | 'o' => $this->entailment['o'],
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| 340 | );
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| 341 | }
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| 342 | }
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| 343 | ?> |
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