001/*
002 *                    BioJava development code
003 *
004 * This code may be freely distributed and modified under the
005 * terms of the GNU Lesser General Public Licence.  This should
006 * be distributed with the code.  If you do not have a copy,
007 * see:
008 *
009 *      http://www.gnu.org/copyleft/lesser.html
010 *
011 * Copyright for this code is held jointly by the individual
012 * authors.  These should be listed in @author doc comments.
013 *
014 * For more information on the BioJava project and its aims,
015 * or to join the biojava-l mailing list, visit the home page
016 * at:
017 *
018 *      http://www.biojava.org/
019 *
020 */
021
022
023package org.biojava.nbio.ontology.utils;
024
025
026
027/**
028 * <p>Indicates that an object has an associated annotation.</p>
029 *
030 * <p>Many BioJava objects will have associated unstructured
031 * data. This should be stored in an Annotation instance. However, the
032 * BioJava object itself will probably not want to extend the
033 * Annotation interface directly, but rather delegate off that
034 * functionality to an Annotation property. The Annotatable interface
035 * indicates that there is an Annotation property. When implementing
036 * Annotatable, you should always create a protected or private field
037 * containing an instance of ChangeForwarder, and register it as a
038 * ChangeListener with the associated Annotation delegate
039 * instance.</p>
040 *
041 * <pre>
042 * public class Foo extends AbstractChangeable implements Annotatable {
043 *   private Annotation ann; // the associated annotation delegate
044 *   protected ChangeForwarder annFor; // the event forwarder
045 *
046 *   public Foo() {
047 *     // make the ann delegate
048 *     ann = new SimpleAnnotation();
049 *     // construct the forwarder so that it emits Annotatable.ANNOTATION ChangeEvents
050 *     // for the Annotation.PROPERTY events it will listen for
051 *     annFor = new ChangeForwarder.Retyper(this, getChangesupport( Annotatable.ANNOTATION ),
052 *                                          Annotatable.ANNOTATION );
053 *     // connect the forwarder so it listens for Annotation.PROPERTY events
054 *     ann.addChangeListener( annFor, Annotation.PROPERTY );
055 *   }
056 *
057 *   public Annotation getAnnotation() {
058 *     return ann;
059 *   }
060 * }
061 * </pre>
062 * Check if BioJava classes and interfaces extend Annotatable. This
063 * will tell  you if you should look for associated annotation.
064 *
065 *  If an object implements Annotatable, it may well propagate
066 * ChangeEvent notifications from the associated Annotation. You may
067 * need to track these to maintain the state of your applications.
068 *
069 * Be careful to hook up the appropriate event forwarders.
070 *
071 * The getAnnotation() method can be implemented lazily
072 * (instantiate the Annotation instance and event forwarders when the first
073 * request comes in). It can also be implemented by returning throw-away
074 * immutable Annotation instances that are built from scratch each time.
075 * @author  Matthew Pocock
076 * @author <a href="mailto:kdj@sanger.ac.uk">Keith James</a> (docs).
077 * @author  Kalle Näslund (docs)
078 * @see org.biojavax.RichAnnotatable
079 * @since 1.0
080 */
081public interface Annotatable  {
082
083
084        /**
085         * Should return the associated annotation object.
086         *
087         * @return an Annotation object, never null
088         */
089        Annotation getAnnotation();
090
091
092}