org.semanticweb.elk.reasoner.saturation.conclusions.classes.DerivedClassConclusionChecker Maven / Gradle / Ivy

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package org.semanticweb.elk.reasoner.saturation.conclusions.classes;

/*-
 * #%L
 * ELK Reasoner Core
 * $Id:$
 * $HeadURL:$
 * %%
 * Copyright (C) 2011 - 2021 Department of Computer Science, University of Oxford
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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import org.semanticweb.elk.reasoner.indexing.classes.DummyIndexedContextRootVisitor;
import org.semanticweb.elk.reasoner.indexing.model.HasNegativeOccurrence;
import org.semanticweb.elk.reasoner.indexing.model.HasPositiveOccurrence;
import org.semanticweb.elk.reasoner.indexing.model.IndexedClassExpression;
import org.semanticweb.elk.reasoner.indexing.model.IndexedComplexClassExpression;
import org.semanticweb.elk.reasoner.indexing.model.IndexedContextRoot;
import org.semanticweb.elk.reasoner.indexing.model.IndexedRangeFiller;
import org.semanticweb.elk.reasoner.indexing.model.IndexedSubObject;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.BackwardLink;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.ClassConclusion;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.ClassInconsistency;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.ContextInitialization;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.DisjointSubsumer;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.ForwardLink;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.Propagation;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.SubClassConclusion;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.SubClassInclusionComposed;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.SubClassInclusionDecomposed;
import org.semanticweb.elk.reasoner.saturation.conclusions.model.SubContextInitialization;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Checks necessary conditions for {@link ClassConclusion} to be derived for the
 * current ontology. The necessary conditions involve, for example, checking if
 * all {@link IndexedSubObject}s of this {@link ClassConclusion} occur in the
 * ontology with proper polarities.
 * 
 * @author "Yevgeny Kazakov"
 */
public class DerivedClassConclusionChecker
		implements ClassConclusion.Visitor {

	private static final ClassConclusion.Visitor INSTANCE_ = new DerivedClassConclusionChecker();

	// logger for this class
	private static final Logger LOGGER_ = LoggerFactory
			.getLogger(DerivedClassConclusionChecker.class);

	/**
	 * Checks the necessary condition for the given {@link ClassConclusion} to
	 * be derived for the current ontology.
	 * 
	 * @param conclusion
	 *            the {@link ClassConclusion} to be checked
	 * @return {@code false} if conclusion cannot be derived for the current
	 *         ontology. If {@code true} is returned, however, this still does
	 *         not mean that conclusion is derivable.
	 */
	public static boolean check(ClassConclusion conclusion) {
		return conclusion.accept(INSTANCE_);
	}

	private final static IndexedContextRoot.Visitor ROOT_OCCURRENCE_CHECKER_ = new DummyIndexedContextRootVisitor() {

		@Override
		protected Boolean defaultVisit(IndexedClassExpression element) {
			return occursPositively(element);
		}

		@Override
		public Boolean visit(IndexedRangeFiller element) {
			return occursPositively(element.getFiller())
					&& occurs(element.getProperty());
		}

	};

	private static boolean occurs(IndexedSubObject iobj) {
		return iobj.occurs();
	}

	private static boolean occurs(IndexedClassExpression iobj) {
		return iobj.occurs();
	}

	private static boolean occurs(IndexedContextRoot root) {
		return root.accept(ROOT_OCCURRENCE_CHECKER_);
	}

	private static boolean occursNegatively(IndexedComplexClassExpression ice) {
		return ice.occursNegatively();
	}

	private static boolean occursNegatively(IndexedSubObject obj) {
		if (obj instanceof HasNegativeOccurrence) {
			return ((HasNegativeOccurrence) obj).occursNegatively();
		}
		// else
		return occurs(obj);
	}

	private static boolean occursPositively(IndexedSubObject obj) {
		if (obj instanceof HasPositiveOccurrence) {
			return ((HasPositiveOccurrence) obj).occursPositively();
		}
		// else
		return occurs(obj);
	}

	private boolean log(ClassConclusion conclusion) {
		LOGGER_.trace("Conclusion could be (re)derived: {}", conclusion);
		return true;
	}

	protected boolean defaultVisit(ClassConclusion conclusion) {
		return occurs(conclusion.getDestination())
				&& occurs(conclusion.getTraceRoot()) && log(conclusion);
	}

	protected boolean defaultVisit(SubClassConclusion conclusion) {
		return occurs(conclusion.getSubDestination())
				&& occurs(conclusion.getTraceRoot())
				&& defaultVisit((ClassConclusion) conclusion);
	}

	@Override
	public Boolean visit(BackwardLink conclusion) {
		return occurs(conclusion.getRelation())
				&& occurs(conclusion.getSource()) && defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(ClassInconsistency conclusion) {
		return defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(ContextInitialization conclusion) {
		return defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(DisjointSubsumer conclusion) {
		return occurs(conclusion.getDisjointExpressions())
				&& defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(ForwardLink conclusion) {
		return occurs(conclusion.getChain()) && occurs(conclusion.getTarget())
				&& defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(Propagation subConclusion) {
		return occurs(subConclusion.getRelation())
				&& occursNegatively(subConclusion.getCarry())
				&& defaultVisit(subConclusion);
	}

	@Override
	public Boolean visit(SubClassInclusionComposed conclusion) {
		return occursNegatively(conclusion.getSubsumer())
				&& defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(SubClassInclusionDecomposed conclusion) {
		return occurs(conclusion.getSubsumer()) && defaultVisit(conclusion);
	}

	@Override
	public Boolean visit(SubContextInitialization conclusion) {
		return defaultVisit(conclusion);
	}

}