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Apache Clerezza API implements the RDF data model as defined by http://www.w3.org/TR/rdf11-concepts/

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/*
 * 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.clerezza;

/**
 * A structure containing a subject, a predicate, and an object.
 * Also known as a statement.
 *
 * @author reto
 */
public interface Triple {

    BlankNodeOrIRI getSubject();

    IRI getPredicate();

    RDFTerm getObject();

    /**
     * @param obj
     * @return true iff subject, predicate, and object of both triples are equal
     */
    @Override
    boolean equals(Object obj);

    /**
     * The hash code is computed as follow
     * (subject.hashCode() >> 1) ^  predicate.hashCode() ^ object.hashCode() << 1)
     * 
     * Note that the hash returned is computed including the hash of BNodes, so
     * it is not blank-node blind as in Graph.
     * 
     * This would have to change if triple should extend Graph
     *
     * @return hash code
     */
    @Override
    int hashCode();
}