| package org.apache.rya.rdftriplestore.inference; |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 limitations |
| * under the License. |
| */ |
| |
| import org.apache.rya.api.RdfCloudTripleStoreConfiguration; |
| import org.eclipse.rdf4j.model.IRI; |
| import org.eclipse.rdf4j.query.algebra.StatementPattern; |
| import org.eclipse.rdf4j.query.algebra.Var; |
| import org.eclipse.rdf4j.query.algebra.ZeroLengthPath; |
| |
| /** |
| * Expands the query tree to account for any relevant reflexive properties |
| * known to the {@link InferenceEngine}. |
| * |
| * A reflexive property is a property for which any node can be inferred to have |
| * reflexively: If :p is a reflexive property, then <?x :p ?x> is true for all ?x. |
| * |
| * Applies to any statement pattern whose predicate is defined (not a variable) |
| * and is a reflexive property according to the InferenceEngine. If the property |
| * is reflexive, then the statement pattern should match when the subject equals |
| * the object. Therefore, replace the statement pattern with a union of itself |
| * and a ZeroLengthPath between the subject and object. This union is similar to |
| * the ZeroOrOnePath property path expression in SPARQL: <?x :p? ?y> matches if |
| * ?x and ?y are connected via :p or if ?x and ?y are equal. |
| */ |
| public class ReflexivePropertyVisitor extends AbstractInferVisitor { |
| /** |
| * Creates a new {@link ReflexivePropertyVisitor}. |
| * @param conf The {@link RdfCloudTripleStoreConfiguration}. |
| * @param inferenceEngine The InferenceEngine containing the relevant ontology. |
| */ |
| public ReflexivePropertyVisitor(RdfCloudTripleStoreConfiguration conf, InferenceEngine inferenceEngine) { |
| super(conf, inferenceEngine); |
| include = conf.isInferReflexiveProperty(); |
| } |
| |
| /** |
| * Check whether any solution for the {@link StatementPattern} could be derived from |
| * reflexive property inference, and if so, replace the pattern with a union of itself and the |
| * reflexive solution. |
| */ |
| @Override |
| protected void meetSP(StatementPattern node) throws Exception { |
| // Only applies when the predicate is defined and reflexive |
| final Var predVar = node.getPredicateVar(); |
| if (predVar.getValue() != null && inferenceEngine.isReflexiveProperty((IRI) predVar.getValue())) { |
| final StatementPattern originalSP = node.clone(); |
| // The reflexive solution is a ZeroLengthPath between subject and |
| // object: they can be matched to one another, whether constants or |
| // variables. |
| final Var subjVar = node.getSubjectVar(); |
| final Var objVar = node.getObjectVar(); |
| final ZeroLengthPath reflexiveSolution = new ZeroLengthPath(subjVar, objVar); |
| node.replaceWith(new InferUnion(originalSP, reflexiveSolution)); |
| } |
| } |
| } |