org.geotools.graph.structure
Interface Graph

All Known Subinterfaces:

DirectedGraph

All Known Implementing Classes:

BasicDirectedGraph, BasicGraph

public interface Graph

Represents a graph. A graph is a collection of nodes (verticies) connected by links called edges (arcs).

In most applications nodes of a graph represent the objects being modelled, and the edges represent the relationships between the objects. An example could be a polygon coverage in which one wishes to model a boundary sharing relationship. The following is an illustration.



In the above figure, the objects (nodes) are the polygons themselves, and the relationship (edges) between them is boundary sharing.

However, there exists types of graphs in which the roles are reversed and the edges are the objects, and the nodes are the relationships. An example of such a graph is the stream network shown below.



In the above figure, the objects (edges) are the stream segments and the relationship (nodes) between them is endpoint sharing. However, if desirable one could model the second case similar to the first. The resulting graph is shown below.



The Graph object is intended to serve as a container for a collection of nodes and edges. It does dont define or manage the relationship among the components it contains.

Author:

Justin Deoliveira, Refractions Research Inc, jdeolive@refractions.net

See Also:

Node, Edge

Field Summary

static int	FAIL_QUERY Signal to indicate that a graph component does NOT meet the requirements of a query made against the graph.
static int	PASS_AND_CONTINUE Signal to indicate that a graph component meets the requirements of a query against a graph and that the query should continue.
static int	PASS_AND_STOP Signal to indicate that a graph component meets the requirements of a query against a graph and that the query should end.

Method Summary

java.util.Collection	getEdges() Returns the edges of the graph.
java.util.Collection	getNodes() Returns the nodes of the graph.
java.util.List	getNodesOfDegree(int n) Returns all the nodes in the graph of a specified degree.
java.util.List	getVisitedEdges(boolean visited) Returns all the edges in the graph that have been marked as visited or non-visited.
java.util.List	getVisitedNodes(boolean visited) Returns all the nodes in the graph that have been marked as visited or non-visited.
java.util.List	queryEdges(GraphVisitor visitor) Performs a query against the edges of the graph.
java.util.List	queryNodes(GraphVisitor visitor) Performs a query against the nodes of the graph.
void	visitEdges(GraphVisitor visitor) Applies the visitor pattern to the edges of the graph.
void	visitNodes(GraphVisitor visitor) Applies the visitor pattern to the nodes of the graph.

Field Detail

PASS_AND_CONTINUE

public static final int PASS_AND_CONTINUE

Signal to indicate that a graph component meets the requirements of a query against a graph and that the query should continue.

See Also:

Constant Field Values

PASS_AND_STOP

public static final int PASS_AND_STOP

Signal to indicate that a graph component meets the requirements of a query against a graph and that the query should end.

See Also:

Constant Field Values

FAIL_QUERY

public static final int FAIL_QUERY

Signal to indicate that a graph component does NOT meet the requirements of a query made against the graph.

See Also:

Constant Field Values

Method Detail

getNodes

public java.util.Collection getNodes()

Returns the nodes of the graph.

Returns:

A collection of Node objects.

See Also:

Node

getEdges

public java.util.Collection getEdges()

Returns the edges of the graph.

Returns:

A collection of Edge objects.

See Also:

Edge

queryNodes

public java.util.List queryNodes(GraphVisitor visitor)

Performs a query against the nodes of the graph. Each Node object contained in the graph is passed to a GraphVisitor to determine if it meets the query criteria.

Parameters:

visitor - Determines if node meets query criteria. Returns MEET_AND_CONTINUE to signal that the node meets the query criteria and the query should continue.
Returns MEET_AND_STOP to signal that the node meest the query criteria and the query should stop.
FAIL_QUERY to signal that the node does NOT meet the query criteria.

Returns:

A collection of nodes that meet the query criteria.

See Also:

Node, GraphVisitor

queryEdges

public java.util.List queryEdges(GraphVisitor visitor)

Performs a query against the edges of the graph. Each Edge object contained in the graph is passed to a GraphVisitor to determine if it meets the query criteria.

Parameters:

visitor - Determines if the meets the query criteria.
Returns MEET_AND_CONTINUE to signal that the edge meets the query criteria and the query should continue.
Returns MEET_AND_STOP to signal that the edge meest the query criteria and the query should stop.
FAIL_QUERY to signal that the edge does NOT meet the query criteria.

Returns:

A collection of edges that meet the query criteria.

See Also:

Edge, GraphVisitor

visitNodes

public void visitNodes(GraphVisitor visitor)

Applies the visitor pattern to the nodes of the graph.

Parameters:

visitor -

visitEdges

public void visitEdges(GraphVisitor visitor)

Applies the visitor pattern to the edges of the graph.

Parameters:

visitor -

getNodesOfDegree

public java.util.List getNodesOfDegree(int n)

Returns all the nodes in the graph of a specified degree. The degree of a node is the number of edges that are adjacent to the node.

Parameters:

n - The desired degree of nodes to be returned.

Returns:

A collection of nodes of degree n.

See Also:

Node.getDegree()

getVisitedNodes

public java.util.List getVisitedNodes(boolean visited)

Returns all the nodes in the graph that have been marked as visited or non-visited.

Parameters:

visited - True if node is visited, false if node is unvisited.

Returns:

List of nodes marked as visited / non-visited.

See Also:

Graphable.isVisited()

getVisitedEdges

public java.util.List getVisitedEdges(boolean visited)

Returns all the edges in the graph that have been marked as visited or non-visited.

Parameters:

visited - True if edge is visited, false if edge is unvisited.

Returns:

List of edges marked as visited / non-visited.

See Also:

Graphable.isVisited()