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Standard interfaces implemented throughout the library.
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/*
 *    GeoTools - The Open Source Java GIS Toolkit
 *    http://geotools.org
 *
 *    (C) 2011, Open Source Geospatial Foundation (OSGeo)
 *    (C) 2004-2007 Open Geospatial Consortium Inc.
 *
 *    All Rights Reserved. http://www.opengis.org/legal/
 */
package org.opengis.feature;

import org.opengis.feature.type.FeatureType;
import org.opengis.filter.identity.FeatureId;
import org.opengis.geometry.BoundingBox;

/**
 * An instance of {@link FeatureType} representing a geographic feature composed of geometric and
 * non-geometric properties.
 *
 * Beyond being a complex attribute, a feature contains the following additional information:
 *
 * 

 *   A default geometry. To be used when drawing when nothing more specific has been provided.
 *   
The bounds of all the geometric attributes of the feature
 * 
 *
 * @see FeatureType
 * @author Jody Garnett (Refractions Research)
 * @author Justin Deoliveira (The Open Planning Project)
 * @since GeoAPI 2.2
 * @version 8.0
 */
public interface Feature extends ComplexAttribute {

    /**
     * Override and type narrow to FeatureType.
     *
     * @return The feature type
     */
    FeatureType getType();

    /**
     * A unique identifier for the feature.
     *
     * getType().isIdentifiable() must return true so this value must
     * not return null.
     *
     * 
Generation of the identifier is dependent on the underlying data storage medium. Often
     * this identifier is not persistent. Mediums such shapefiles and database tables have "keys"
     * built in which map naturally to persistent feature identifiers. But other mediums do not have
     * such keys and may have to generate feature identifiers "on-the-fly". This means that client
     * code being able to depend on this value as a persistent entity is dependent on which storage
     * medium or data source is being used.
     *
     * @return The feature identifier, never null.
     */
    FeatureId getIdentifier();

    /**
     * The bounds of this Feature, if available.
     *
     * 
This value is derived from any geometric attributes that the feature is composed of.
     *
     * 
In the case that the feature has no geometric attributes this method should return an
     * empty bounds, ie, bounds.isEmpty() == true. This method should never return
     * null.
     *
     * 
The coordinate reference system of the returned bounds is derived from the geometric
     * attributes which were used to compute the bounds. In the event that the feature contains
     * multiple geometric attributes which have different crs's, the one defined by {@link
     * #getGeometryDescriptor()} should take precedence and the others should be reprojected
     * accordingly.
     *
     * @return the feature bounds, possibly empty.
     */
    BoundingBox getBounds();

    /**
     * The default geometric attribute of the feature.
     *
     * 
This method returns null in the case where no such attribute exists.
     *
     * @return The default geometry attribute, or null.
     */
    GeometryAttribute getDefaultGeometryProperty();

    /**
     * Sets the default geometric attribute of the feature.
     *
     * This value must be an attribute which is already defined for the feature. In other words,
     * this method can not be used to add a new attribute to the feature.
     *
     * @param geometryAttribute The new geomtric attribute.
     * @throws IllegalArgumentException If the specified attribute is not already an attribute of
     *     the feature.
     */
    void setDefaultGeometryProperty(GeometryAttribute geometryAttribute);
}