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Java > Open Source Codes > com > hp > hpl > jena > reasoner > rulesys > impl > oldCode > GoalState


1 /******************************************************************
2  * File: GoalState.java
3  * Created by: Dave Reynolds
4  * Created on: 04-May-2003
5  *
6  * (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP
7  * [See end of file]
8  * $Id: GoalState.java,v 1.5 2005/02/21 12:18:04 andy_seaborne Exp $
9  *****************************************************************/
10 package com.hp.hpl.jena.reasoner.rulesys.impl.oldCode;
11
12 import com.hp.hpl.jena.reasoner.rulesys.impl.StateFlag;
13 import com.hp.hpl.jena.util.iterator.ClosableIterator;
14 import org.apache.commons.logging.Log;
15 import org.apache.commons.logging.LogFactory;
16
17 /**
18  * Represents the state in a traversal of all the solutions of a
19  * given goal. This will traverse, in turn, all the matches in the
20  * underlying triple stores, all the memoized results currently in
21  * the GoalTable and then all the additional results which can be
22  * found by turns of the goal Generator crank, until the goal (or the
23  * whole derivation) is complete.
24  *
25  * @author <a HREF="mailto:der@hplb.hpl.hp.com">Dave Reynolds</a>
26  * @version $Revision: 1.5 $ on $Date: 2005/02/21 12:18:04 $
27  */
28 public class GoalState {
29     
30     /** An iterator over the matching triples in the stores */
31     protected ClosableIterator tripleMatches;
32     
33     /** The goal table entry for this goal */
34     protected GoalResults results;
35     
36     /** The index of the next memoized solution to return */
37     protected int solutionPointer = 0;
38     
39     static Log logger = LogFactory.getLog(GoalState.class);
40     
41     /**
42      * Constructor. Create a GoalState which can traverse all the
43      * matches to a goal over a set of raw data plus derivations.
44      * @param tripleMatches an interation over the raw data results
45      * @param results a GoalResults which gives access to memoized
46      * results for this goal together with the Generator that can
47      * produce additional results
48      */
49     public GoalState(ClosableIterator tripleMatches, GoalResults results) {
50         this.tripleMatches = tripleMatches;
51         this.results = results;
52     }
53
54     /**
55      * Return the GoalResults entry which this state is built in
56      */
57     public GoalResults getGoalResultsEntry() {
58         return results;
59     }
60     
61     /**
62      * Return the next available result for this goal.
63      * @return a Triple matching the goal if there is another result available,
64      * or FAIL if there are known to be no more matches or SUSPEND if there
65      * may be more results in the future but current progress is blocked waiting
66      * for other subgoals.
67      */
68     public Object JavaDoc next() {
69         if (tripleMatches != null) {
70             if (tripleMatches.hasNext()) {
71                 return tripleMatches.next();
72             } else {
73                 tripleMatches = null;
74             }
75         }
76         if (solutionPointer < results.numResults()) {
77             return results.getResult(solutionPointer++);
78         } else if (results.isComplete() ){
79             return StateFlag.FAIL;
80         } else {
81             // No more results yet, the caller should block
82 return StateFlag.SUSPEND;
83         }
84     }
85     
86     /**
87      * Return true if there seems to be at least one new result available or if
88      * this can be stripped off the agenda because it has failed.
89      */
90     public boolean couldProcess() {
91         if (tripleMatches != null && tripleMatches.hasNext()) return true;
92         if (results.started && solutionPointer < results.numResults()) return true;
93         if (results.isComplete) return true;
94         return false;
95     }
96     
97     /**
98      * Close the GoalState, closing any still active iterators.
99      */
100     public void close() {
101         if (tripleMatches != null) {
102             tripleMatches.close();
103             tripleMatches = null;
104         }
105     }
106     
107     /**
108      * Printable form
109      */
110     public String JavaDoc toString() {
111         return "GoalState(" + results.goal.toString() + ")";
112     }
113
114 }
115
116
117
118 /*
119     (c) Copyright 2003, 2004, 2005 Hewlett-Packard Development Company, LP
120     All rights reserved.
121
122     Redistribution and use in source and binary forms, with or without
123     modification, are permitted provided that the following conditions
124     are met:
125
126     1. Redistributions of source code must retain the above copyright
127        notice, this list of conditions and the following disclaimer.
128
129     2. Redistributions in binary form must reproduce the above copyright
130        notice, this list of conditions and the following disclaimer in the
131        documentation and/or other materials provided with the distribution.
132
133     3. The name of the author may not be used to endorse or promote products
134        derived from this software without specific prior written permission.
135
136     THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
137     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
138     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
139     IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
140     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
141     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
142     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
143     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
144     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
145     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
146 */
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