001/*
002 *    GeoAPI - Java interfaces for OGC/ISO standards
003 *    Copyright © 2004-2023 Open Geospatial Consortium, Inc.
004 *    http://www.geoapi.org
005 *
006 *    Licensed under the Apache License, Version 2.0 (the "License");
007 *    you may not use this file except in compliance with the License.
008 *    You may obtain a copy of the License at
009 *
010 *        http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *    Unless required by applicable law or agreed to in writing, software
013 *    distributed under the License is distributed on an "AS IS" BASIS,
014 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 *    See the License for the specific language governing permissions and
016 *    limitations under the License.
017 */
018package org.opengis.metadata.identification;
019
020import java.util.Collection;
021import org.opengis.util.InternationalString;
022import org.opengis.metadata.citation.Citation;
023import org.opengis.annotation.UML;
024
025import static org.opengis.annotation.Obligation.*;
026import static org.opengis.annotation.Specification.*;
027
028
029/**
030 * Keywords, their type and reference source.
031 *
032 * <div class="note"><b>Note:</b>
033 * when the resource described is a service, one instance of {@code Keywords} should refer to the
034 * service taxonomy defined in ISO 191119.</div>
035 *
036 * @author  Martin Desruisseaux (IRD)
037 * @author  Rémi Maréchal (Geomatys)
038 * @version 3.1
039 * @since   2.0
040 */
041@UML(identifier="MD_Keywords", specification=ISO_19115)
042public interface Keywords {
043    /**
044     * Commonly used word(s) or formalised word(s) or phrase(s) used to describe the subject.
045     *
046     * @return word(s) or phrase(s) used to describe the subject.
047     */
048    @UML(identifier="keyword", obligation=MANDATORY, specification=ISO_19115)
049    Collection<? extends InternationalString> getKeywords();
050
051    /**
052     * Subject matter used to group similar keywords.
053     *
054     * @return subject matter used to group similar keywords, or {@code null}.
055     */
056    @UML(identifier="type", obligation=OPTIONAL, specification=ISO_19115)
057    default KeywordType getType() {
058        return null;
059    }
060
061    /**
062     * Name of the formally registered thesaurus or a similar authoritative source of keywords.
063     *
064     * @return name of registered thesaurus or similar authoritative source of keywords, or {@code null}.
065     */
066    @UML(identifier="thesaurusName", obligation=OPTIONAL, specification=ISO_19115)
067    default Citation getThesaurusName() {
068        return null;
069    }
070
071    /**
072     * User-defined categorization of groups of keywords that extend or are orthogonal
073     * to the standardized {@linkplain #getType() keyword type} codes.
074     * Keyword classes are associated with on ontology that allow additional semantic
075     * query processing.
076     *
077     * <div class="note"><b>Note:</b>
078     * the {@linkplain #getThesaurusName() thesaurus citation} specifies a collection of instances from some ontology,
079     * but is not an ontology. It might be a list of places that include rivers, mountains, counties and cities.
080     * There might be a Laconte county, the city of Laconte, the Laconte River, and Mt. Laconte;
081     * when searching it is useful for the user to be able to restrict the search to only rivers.
082     * </div>
083     *
084     * @return user-defined categorization of groups of keywords, or {@code null} if none.
085     *
086     * @since 3.1
087     */
088    @UML(identifier="keywordClass", obligation=OPTIONAL, specification=ISO_19115)
089    default KeywordClass getKeywordClass() {
090        return null;
091    }
092}