/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2011, Open Source Geospatial Foundation (OSGeo)
* (C) 2005 Open Geospatial Consortium Inc.
*
* All Rights Reserved. http://www.opengis.org/legal/
*/
package org.opengis.filter;
// OpenGIS direct dependencies
import org.opengis.annotation.XmlElement;
import org.opengis.filter.expression.Expression;
/**
* Filter operator that checks if an expression's value is {@code null}. A {@code null}
* is equivalent to no value present. The value 0 is a valid value and is not considered
* {@code null}.
*
*
* @source $URL: http://svn.osgeo.org/geotools/trunk/modules/library/opengis/src/main/java/org/opengis/filter/PropertyIsNull.java $
* @version <A HREF="http://www.opengis.org/docs/02-059.pdf">Implementation specification 1.0</A>
* @author Chris Dillard (SYS Technologies)
* @since GeoAPI 2.0
*/
@XmlElement("PropertyIsNull")
public interface PropertyIsNull extends Filter {
/** Operator name used to check FilterCapabilities */
public static String NAME = "NullCheck";
/**
* Returns the expression whose value will be checked for {@code null}.
*/
@XmlElement("PropertyName")
Expression getExpression();
}