| /** |
| * 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. |
| */ |
| package org.apache.commons.rdf.api; |
| |
| import java.util.Objects; |
| |
| /** |
| * An <a href= "http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple" >RDF-1.1 |
| * Triple</a>, as defined by |
| * <a href= "http://www.w3.org/TR/rdf11-concepts/#section-triples" >RDF-1.1 Concepts and |
| * Abstract Syntax</a>, a W3C Recommendation published on 25 February 2014. |
| * <p> |
| * A <code>Triple</code> object in Commons RDF is considered |
| * <strong>immutable</strong>, that is, over its life time it will have |
| * consistent behaviour for its {@link #equals(Object)}, and the {@link RDFTerm} |
| * instances returned from {@link #getSubject()}, {@link #getPredicate()} and |
| * {@link #getObject()} will have consistent {@link RDFTerm#equals(Object)} |
| * behaviour. |
| * <p> |
| * Note that <code>Triple</code> methods are not required to return object |
| * identical (<code>==</code>) instances as long as they are equivalent |
| * according to {@link RDFTerm#equals(Object)}. Specialisations of |
| * <code>Triple</code> may provide additional methods that are documented to be |
| * mutable. |
| * <p> |
| * <code>Triple</code> methods are <strong>thread-safe</strong>, however |
| * specialisations may provide additional methods that are documented to not be |
| * thread-safe. |
| * <p> |
| * <code>Triple</code>s can be safely used in hashing collections like |
| * {@link java.util.HashSet} and {@link java.util.HashMap}. |
| * <p> |
| * Any <code>Triple</code> can be used interchangeably across Commons RDF |
| * implementations. |
| * |
| * @see Quad |
| * @see RDF#createTriple(BlankNodeOrIRI,IRI,RDFTerm) |
| * @see <a href= "http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-triple" >RDF-1.1 |
| * Triple</a> |
| */ |
| public interface Triple extends TripleLike { |
| |
| /** |
| * The subject of this triple, which may be either a {@link BlankNode} or an |
| * {@link IRI}, which are represented in Commons RDF by the interface |
| * {@link BlankNodeOrIRI}. |
| * |
| * @return The subject {@link BlankNodeOrIRI} of this triple. |
| * @see <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-subject">RDF-1.1 |
| * Triple subject</a> |
| */ |
| @Override |
| BlankNodeOrIRI getSubject(); |
| |
| /** |
| * The predicate {@link IRI} of this triple. |
| * |
| * @return The predicate {@link IRI} of this triple. |
| * @see <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-predicate">RDF-1.1 |
| * Triple predicate</a> |
| */ |
| @Override |
| IRI getPredicate(); |
| |
| /** |
| * The object of this triple, which may be either a {@link BlankNode}, an |
| * {@link IRI}, or a {@link Literal}, which are represented in Commons RDF |
| * by the interface {@link RDFTerm}. |
| * |
| * @return The object {@link RDFTerm} of this triple. |
| * @see <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-object">RDF-1.1 |
| * Triple object</a> |
| */ |
| @Override |
| RDFTerm getObject(); |
| |
| /** |
| * Check it this Triple is equal to another Triple. |
| * <p> |
| * Two Triples are equal if and only if their {@link #getSubject()}, |
| * {@link #getPredicate()} and {@link #getObject()} are equal. |
| * </p> |
| * <p> |
| * Implementations MUST also override {@link #hashCode()} so that two equal |
| * Triples produce the same hash code. |
| * </p> |
| * |
| * @param other |
| * Another object |
| * @return true if other is a Triple and is equal to this |
| * @see Object#equals(Object) |
| */ |
| @Override |
| boolean equals(Object other); |
| |
| /** |
| * Calculate a hash code for this Triple. |
| * <p> |
| * The returned hash code MUST be equal to the result of |
| * {@link Objects#hash(Object...)} with the arguments {@link #getSubject()}, |
| * {@link #getPredicate()}, {@link #getObject()}. |
| * <p> |
| * This method MUST be implemented in conjunction with |
| * {@link #equals(Object)} so that two equal {@link Triple}s produce the |
| * same hash code. |
| * |
| * @return a hash code value for this Triple. |
| * @see Object#hashCode() |
| * @see Objects#hash(Object...) |
| */ |
| @Override |
| int hashCode(); |
| |
| } |