| /** |
| * 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.UUID; |
| |
| /** |
| * A <a href= "http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node" >RDF-1.1 |
| * Blank Node</a>, as defined by |
| * <a href= "http://www.w3.org/TR/rdf11-concepts/#section-blank-nodes" >RDF-1.1 |
| * Concepts and Abstract Syntax</a>, a W3C Recommendation published on 25 |
| * February 2014.<br> |
| * |
| * Note: <blockquote> |
| * <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node">Blank nodes</a> |
| * are disjoint from IRIs and literals. Otherwise, the set of possible blank |
| * nodes is arbitrary. RDF makes no reference to any internal structure of blank |
| * nodes. </blockquote> |
| * |
| * Also note that: <blockquote> <a href= |
| * "http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node-identifier">Blank node |
| * identifiers</a> are local identifiers that are used in some concrete RDF |
| * syntaxes or RDF store implementations. They are always <em>locally |
| * scoped</em> to the file or RDF store, and are <em>not</em> persistent or |
| * portable identifiers for blank nodes. Blank node identifiers are <em>not</em> |
| * part of the RDF abstract syntax, but are entirely dependent on the concrete |
| * syntax or implementation. The syntactic restrictions on blank node |
| * identifiers, if any, therefore also depend on the concrete RDF syntax or |
| * implementation. |
| * |
| * Implementations that handle blank node identifiers in concrete syntaxes need |
| * to be careful not to create the same blank node from multiple occurrences of |
| * the same blank node identifier except in situations where this is supported |
| * by the syntax. </blockquote> |
| * |
| * A BlankNode SHOULD contain a {@link UUID}-derived string as part of its |
| * universally unique {@link #uniqueReference()}. |
| * |
| * @see RDF#createBlankNode() |
| * @see RDF#createBlankNode(String) |
| * @see <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node">RDF-1.1 |
| * Blank Node</a> |
| */ |
| public interface BlankNode extends BlankNodeOrIRI { |
| |
| /** |
| * Return a reference for uniquely identifying the blank node. |
| * <p> |
| * The reference string MUST universally and uniquely identify this blank |
| * node. That is, different blank nodes created separately in different JVMs |
| * or from different {@link RDF} instances MUST NOT have the same reference |
| * string. |
| * <p> |
| * The {@link #uniqueReference()} of two <code>BlankNode</code> instances |
| * MUST be equal if and only if the two blank nodes are equal according to |
| * {@link #equals(Object)}. |
| * <p> |
| * Clients should not assume any particular structure of the reference |
| * string, however it is recommended that the reference string contain a |
| * UUID-derived string, e.g. as returned from {@link UUID#toString()}. |
| * <p> |
| * <strong>IMPORTANT:</strong> This is not a |
| * <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node-identifier"> |
| * blank node identifier</a> nor a serialization/syntax label, and there are |
| * no guarantees that it is a valid identifier in any concrete RDF syntax. |
| * For an N-Triples compatible identifier, use {@link #ntriplesString()}. |
| * |
| * @return A universally unique reference to identify this {@link BlankNode} |
| */ |
| String uniqueReference(); |
| |
| /** |
| * Check it this BlankNode is equal to another BlankNode. Two BlankNodes |
| * MUST be equal if, and only if, they have the same |
| * {@link #uniqueReference()}. |
| * <p> |
| * Implementations MUST also override {@link #hashCode()} so that two equal |
| * Literals produce the same hash code. |
| * |
| * @param other |
| * Another object |
| * @return true if other is a BlankNode instance that represent the same |
| * blank node |
| * @see Object#equals(Object) |
| */ |
| @Override |
| boolean equals(Object other); |
| |
| /** |
| * Calculate a hash code for this BlankNode. |
| * <p> |
| * The returned hash code MUST be equal to the {@link String#hashCode()} of |
| * the {@link #uniqueReference()}. |
| * <p> |
| * This method MUST be implemented in conjunction with |
| * {@link #equals(Object)} so that two equal BlankNodes produce the same |
| * hash code. |
| * |
| * @return a hash code value for this BlankNode. |
| * @see Object#hashCode() |
| */ |
| @Override |
| int hashCode(); |
| |
| } |