net.sf.tweety.logics.commons.analysis.AbstractMusEnumerator Maven / Gradle / Ivy

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/*
 *  This file is part of "Tweety", a collection of Java libraries for
 *  logical aspects of artificial intelligence and knowledge representation.
 *
 *  Tweety is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License version 3 as
 *  published by the Free Software Foundation.
 *
 *  This program 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program. If not, see .
 *
 *  Copyright 2016 The Tweety Project Team 
 */
package net.sf.tweety.logics.commons.analysis;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import net.sf.tweety.commons.BeliefSet;
import net.sf.tweety.commons.Formula;
import net.sf.tweety.commons.util.SetTools;

/**
 * Abstract implementation for MUes enumerators.
 * 
 * @author Matthias Thimm
 *
 * @param  the type of formulas
 */
public abstract class AbstractMusEnumerator implements MusEnumerator {

	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#minimalInconsistentSubsets(java.util.Collection)
	 */
	@Override
	public abstract Collection> minimalInconsistentSubsets(Collection formulas);
	
	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#minimalCorrectionSubsets(java.util.Collection)
	 */
	public Set> minimalCorrectionSubsets(Collection formulas){
		// we use the duality of minimal inconsistent subsets, minimal correction sets, and maximal consistent
		// subsets to compute the set of maximal consistent subsets
		Collection> mis = this.minimalInconsistentSubsets(formulas);
		// makes sets out of this
		Set> mi_sets = new HashSet>();
		for(Collection m: mis)
			mi_sets.add(new HashSet(m));
		SetTools settools = new SetTools();
		// get the minimal correction sets, i.e. irreducible hitting sets of minimal inconsistent subsets
		Set> md_sets =  settools.irreducibleHittingSets(mi_sets);
		return md_sets;
	}
	
	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#maximalConsistentSubsets(java.util.Collection)
	 */
	@Override
	public Collection> maximalConsistentSubsets(Collection formulas){
		Set> md_sets = this.minimalCorrectionSubsets(formulas);
		// every maximal consistent subset is the complement of a minimal correction set
		Set> result = new HashSet>();;
		Set tmp;
		for(Collection ms: md_sets){
			tmp = new HashSet(formulas);
			tmp.removeAll(ms);
			result.add(tmp);
		}			
		return result;
	}

	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#isConsistent(net.sf.tweety.BeliefSet)
	 */
	@Override
	public boolean isConsistent(BeliefSet beliefSet){
		return this.isConsistent((Collection) beliefSet);
	}

	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#isConsistent(net.sf.tweety.Formula)
	 */
	@Override
	public boolean isConsistent(S formula){
		Collection c = new HashSet();
		c.add(formula);
		return this.isConsistent(c);
	}

	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#isConsistent(java.util.Collection)
	 */
	@Override
	public boolean isConsistent(Collection formulas){
		return this.minimalInconsistentSubsets(formulas).isEmpty();
	}
	
	/* (non-Javadoc)
	 * @see net.sf.tweety.logics.commons.analysis.MusEnumerator#getMiComponents(java.util.Collection)
	 */
	public Collection> getMiComponents(Collection formulas){
		List> comp = new LinkedList>(this.minimalInconsistentSubsets(formulas));
		boolean changed;
		do{
			changed = false;
			for(int i = 0; i < comp.size(); i++){
				for(int j = i+1; j< comp.size(); j++){
					if(!Collections.disjoint(comp.get(i), comp.get(j))){
						changed = true;
						comp.get(i).addAll(comp.get(j));
						comp.remove(j);
						break;
					}					
				}
				if(changed) break;
			}
		}while(changed);
		return comp;
	}
}