/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.graph.structure;
/**
* Represents a directed graph.
*
* In a directed graph, components have an explicit direction associated with
* them. <BR/>
* <BR/>
* Directed nodes differentiate between those
* adjacent edges that originate at them (outgoing edges ) and those that
* terminate at them (incoming edges).<BR/>
* <BR/>
* Directed edges differentiate between the node at the
* the source of the edge (source node) and the node at the destination of the
* edges (destination node).<BR/>
* <BR/>
* The following is a figure of an undirected graph, and one of the possible
* directed graphs that can be derived from it. Directionality is indicated
* by arrow heads on the edges of the graph.<BR/>
* <BR/>
* <IMG src="doc-files/undirected2directed.gif"><BR/>
* <BR/>
* The following information summarizes the relationships in the directed
* version of the graph.<BR/>
* <BR/>
* <TABLE border="1">
* <TH>Edge</TH>
* <TH>Source Node</TH>
* <TH>Destination Node</TH>
* <TR align="center"><TD>A</TD><TD>1</TD><TD>4</TD></TR>
* <TR align="center"><TD>B</TD><TD>2</TD><TD>4</TD></TR>
* <TR align="center"><TD>C</TD><TD>3</TD><TD>4</TD></TR>
* <TR align="center"><TD>D</TD><TD>4</TD><TD>5</TD></TR>
* <TR align="center"><TD>E</TD><TD>4</TD><TD>7</TD></TR>
* <TR align="center"><TD>F</TD><TD>4</TD><TD>6</TD></TR>
* <TR align="center"><TD>G</TD><TD>5</TD><TD>7</TD></TR>
* <TR align="center"><TD>H</TD><TD>6</TD><TD>7</TD></TR>
* </TABLE><BR/>
* <BR/>
* <TABLE border="1">
* <TH>Node</TH>
* <TH>In Edges</TH>
* <TH>Out Edges</TH>
* <TR align="center"><TD>1</TD><TD> </TD><TD>A</TD></TR>
* <TR align="center"><TD>2</TD><TD> </TD><TD>B</TD></TR>
* <TR align="center"><TD>3</TD><TD> </TD><TD>C</TD></TR>
* <TR align="center"><TD>4</TD><TD>A,B,C</TD><TD>D,E,F</TD></TR>
* <TR align="center"><TD>5</TD><TD>D</TD><TD>G</TD></TR>
* <TR align="center"><TD>6</TD><TD>F</TD><TD>F</TD></TR>
* <TR align="center"><TD>7</TD><TD>E,G,H</TD><TD> </TD></TR>
* </TABLE>
*
* @see DirectedNode
* @see DirectedEdge
*
* @author Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net
*
*
* @source $URL$
*/
public interface DirectedGraph extends Graph {
}