/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2011, Open Source Geospatial Foundation (OSGeo)
 *    (C) 2003-2005, Open Geospatial Consortium Inc.
 *    
 *    All Rights Reserved. http://www.opengis.org/legal/
 */
package org.opengis.referencing.operation;

import org.opengis.referencing.crs.CoordinateReferenceSystem;
import org.opengis.annotation.UML;
import static org.opengis.annotation.Obligation.*;
import static org.opengis.annotation.Specification.*;


/**
 * An operation on coordinates that does not include any change of Datum. The best-known
 * example of a coordinate conversion is a map projection. The parameters describing
 * coordinate conversions are defined rather than empirically derived.
 * <p>
 * Note that some conversions have no parameters.
 *
 *
 * @source $URL: http://svn.osgeo.org/geotools/trunk/modules/library/opengis/src/main/java/org/opengis/referencing/operation/Conversion.java $
 * @version <A HREF="http://portal.opengeospatial.org/files/?artifact_id=6716">Abstract specification 2.0</A>
 * @author  Martin Desruisseaux (IRD)
 * @since   GeoAPI 1.0
 *
 * @see Transformation
 */
@UML(identifier="CC_Conversion", specification=ISO_19111)
public interface Conversion extends Operation {
    /**
     * Returns the source CRS. Conversions may have a source CRS that
     * is not specified here, but through
     * {@link org.opengis.referencing.crs.GeneralDerivedCRS#getBaseCRS} instead.
     *
     * @return The source CRS, or {@code null} if not available.
     */
    @UML(identifier="sourceCRS", obligation=OPTIONAL, specification=ISO_19111)
    CoordinateReferenceSystem getSourceCRS();

    /**
     * Returns the target CRS. {@linkplain Conversion Conversions} may have a target CRS
     * that is not specified here, but through
     * {@link org.opengis.referencing.crs.GeneralDerivedCRS} instead.
     *
     * @return The target CRS, or {@code null} if not available.
     */
    @UML(identifier="targetCRS", obligation=OPTIONAL, specification=ISO_19111)
    CoordinateReferenceSystem getTargetCRS();

    /**
     * This attribute is declared in {@link CoordinateOperation} but is not used in a conversion.
     *
     * @return Always {@code null}.
     */
    @UML(identifier="operationVersion", obligation=CONDITIONAL, specification=ISO_19111)
    String getOperationVersion();
}