001/* Copyright (C) 2013 TU Dortmund
002 * This file is part of LearnLib, http://www.learnlib.de/.
003 * 
004 * LearnLib is free software; you can redistribute it and/or
005 * modify it under the terms of the GNU Lesser General Public
006 * License version 3.0 as published by the Free Software Foundation.
007 * 
008 * LearnLib is distributed in the hope that it will be useful,
009 * but WITHOUT ANY WARRANTY; without even the implied warranty of
010 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
011 * Lesser General Public License for more details.
012 * 
013 * You should have received a copy of the GNU Lesser General Public
014 * License along with LearnLib; if not, see
015 * <http://www.gnu.de/documents/lgpl.en.html>.
016 */
017package de.learnlib.cache.dfa;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.List;
022
023import net.automatalib.incremental.dfa.Acceptance;
024import net.automatalib.incremental.dfa.IncrementalDFABuilder;
025import net.automatalib.words.Alphabet;
026import de.learnlib.api.MembershipOracle;
027import de.learnlib.api.Query;
028
029
030/**
031 * DFA cache. This cache is implemented as a membership oracle: upon construction, it is
032 * provided with a delegate oracle. Queries that can be answered from the cache are answered
033 * directly, others are forwarded to the delegate oracle. When the delegate oracle has finished
034 * processing these remaining queries, the results are incorporated into the cache.
035 * 
036 * @author Malte Isberner <malte.isberner@gmail.com>
037 *
038 * @param <I> input symbol class
039 */
040public class DFACacheOracle<I> implements MembershipOracle<I, Boolean> {
041        
042        private final IncrementalDFABuilder<I> incDfa;
043        private final MembershipOracle<I,Boolean> delegate;
044
045        /**
046         * Constructor.
047         * @param alphabet the alphabet of the cache
048         * @param delegate the delegate oracle
049         */
050        public DFACacheOracle(Alphabet<I> alphabet, MembershipOracle<I,Boolean> delegate) {
051                this.incDfa = new IncrementalDFABuilder<>(alphabet);
052                this.delegate = delegate;
053        }
054        
055        public int getCacheSize() {
056                return incDfa.size();
057        }
058        
059        /**
060         * Creates an equivalence oracle that checks an hypothesis for consistency with the
061         * contents of this cache. Note that the returned oracle is backed by the cache data structure,
062         * i.e., it is sufficient to call this method once after creation of the cache.
063         * @return the cache consistency test backed by the contents of this cache.
064         */
065        public DFACacheConsistencyTest<I> createCacheConsistencyTest() {
066                return new DFACacheConsistencyTest<>(incDfa);
067        }
068        
069        /*
070         * (non-Javadoc)
071         * @see de.learnlib.api.MembershipOracle#processQueries(java.util.Collection)
072         */
073        @Override
074        public void processQueries(Collection<? extends Query<I, Boolean>> queries) {
075                List<ProxyQuery<I>> unanswered = new ArrayList<>();
076                
077                for(Query<I,Boolean> q : queries) {
078                        Acceptance acc = incDfa.lookup(q.getInput());
079                        if(acc != Acceptance.DONT_KNOW)
080                                q.answer((acc == Acceptance.TRUE) ? true : false);
081                        else
082                                unanswered.add(new ProxyQuery<>(q));
083                }
084                
085                delegate.processQueries(unanswered);
086                
087                for(ProxyQuery<I> q : unanswered)
088                        incDfa.insert(q.getInput(), q.getAnswer());
089        }
090
091}