1 /** 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 package org.apache.commons.rdf.api; 19 20 import java.util.Optional; 21 22 /** 23 * A generalised "quad-like" interface, extended by {@link Quad}. 24 * <p> 25 * A QuadLike statement has at least a {@link #getSubject()}, 26 * {@link #getPredicate()}, {@link #getObject()} and {@link #getGraphName()}, 27 * but unlike a {@link Quad} does not have a formalised 28 * {@link Quad#equals(Object)} or {@link Quad#hashCode()} semantics and is not 29 * required to be <em>immutable</em> or <em>thread-safe</em>. This interface can 30 * also be used for <em>generalised quads</em> (e.g. a {@link BlankNode} as 31 * predicate). 32 * <p> 33 * Implementations should specialise which specific {@link RDFTerm} types they 34 * return by overriding {@link #getSubject()}, {@link #getPredicate()}, 35 * {@link #getObject()} and {@link #getGraphName()}. 36 * 37 * @since 0.3.0-incubating 38 * @see Quad 39 */ 40 public interface QuadLike<G extends RDFTerm> extends TripleLike { 41 42 /** 43 * The graph name (graph label) of this statement, if present. 44 * <p> 45 * If {@link Optional#isPresent()}, then the {@link Optional#get()} indicate 46 * the graph name of this statement. If the graph name is not present,e.g. 47 * the value is {@link Optional#empty()}, it indicates that this Quad is in 48 * the default graph. 49 * 50 * @return If {@link Optional#isPresent()}, the graph name of this quad, 51 * otherwise {@link Optional#empty()}, indicating the default graph. 52 * The graph name is typically an {@link IRI} or {@link BlankNode}. 53 */ 54 Optional<G> getGraphName(); 55 56 }