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 }