/*
* 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.geometry.primitive;
import java.util.List;
import org.opengis.annotation.UML;
import static org.opengis.annotation.Obligation.*;
import static org.opengis.annotation.Specification.*;
/**
* The boundary of {@linkplain Surface surfaces}. A {@code SurfaceBoundary} consists of some number
* of {@linkplain Ring rings}, corresponding to the various components of its boundary. In the normal 2D
* case, one of these rings is distinguished as being the exterior boundary. In a general manifold this
* is not always possible, in which case all boundaries shall be listed as interior boundaries,
* and the exterior will be empty.
*
* <blockquote><font size=2>
* <strong>NOTE:</strong> The use of exterior and interior here is not intended to invoke the
* definitions of "interior" and "exterior" of geometric objects. The terms are in common usage,
* and reflect a linguistic metaphor that uses the same linguistic constructs for the concept of
* being inside an object to being inside a container. In normal mathematical terms, the exterior
* boundary is the one that appears in the Jordan Separation Theorem (Jordan Curve Theorem extended
* beyond 2D). The exterior boundary is the one that separates the surface (or solid in 3D) from
* infinite space. The interior boundaries separate the object at hand from other bounded objects.
* The uniqueness of the exterior comes from the uniqueness of unbounded space. Essentially, the
* Jordan Separation Theorem shows that normal 2D or 3D space separates into bounded and unbounded
* pieces by the insertion of a ring or shell, respectively. It goes beyond that, but this
* specification is restricted to at most 3 dimensions.
* <p>
* <strong>EXAMPLE 1:</strong> If the underlying manifold is an infinite cylinder, then two
* transverse cuts of the cylinder define a compact surface between the cuts, and two separate
* unbounded portions of the cylinders. In this case, either cut could reasonably be called
* exterior. In cases of such ambiguity, the standard chooses to list all boundaries in the
* "interior" set. The only guarantee of an exterior boundary being unique is in the 2-dimensional
* plane, E<sup>2</sup>.
* <p>
* <strong>EXAMPLE 2:</strong> Taking the equator of a sphere, and generating a 1 meter buffer,
* we have a surface with two isomorphic boundary components. There is no unbiased manner to
* distinguish one of these as an exterior.
* </font></blockquote>
*
*
* @source $URL: http://svn.osgeo.org/geotools/trunk/modules/library/opengis/src/main/java/org/opengis/geometry/primitive/SurfaceBoundary.java $
* @version <A HREF="http://www.opengeospatial.org/standards/as">ISO 19107</A>
* @author Martin Desruisseaux (IRD)
* @since GeoAPI 1.0
*
* @see SolidBoundary
*/
@UML(identifier="GM_SurfaceBoundary", specification=ISO_19107)
public interface SurfaceBoundary extends PrimitiveBoundary {
/**
* Returns the exterior ring, or {@code null} if none.
*
* @return The exterior ring, or {@code null}.
*/
@UML(identifier="exterior", obligation=MANDATORY, specification=ISO_19107)
Ring getExterior();
/**
* Returns the interior rings.
*
* @return The interior rings. Never {@code null}, but may be an empty array.
*
* @todo Consider using a Collection return type instead.
*/
@UML(identifier="interior", obligation=MANDATORY, specification=ISO_19107)
List<Ring> getInteriors();
}