Hi,
interesting application! I'll supply some example code of how it could
look like.
Assume the neo4j is set up as follows:
public enum MyRelationshipTypes implements RelationshipType
{
CONNECTION,
}
NeoService neo = new EmbeddedNeo( "neo" );
Some code:
(1) Stations
private Node createStation( String name )
{
Node station = neo.createNode();
station.setProperty( "name", name );
return station;
}
Node stationA = createStation( "A" );
Node stationB = createStation( "B" );
Node stationC = createStation( "C" );
Node stationD = createStation( "D" );
Node stationE = createStation( "E" );
(2)-(4) Connections
private Relationship connectStations( Node start, Node end, String pathName )
{
Relationship connection = start.createRelationshipTo( end,
MyRelationshipTypes.CONNECTION );
connection.setProperty( "path", pathName );
return connection;
}
// The departure/arrival properties should be set on the relationship itself
// (how to handle multiple dep/arr of a connection?). They are here for
// demonstration only.
Relationship connectionAB = connectStations( stationA, stationB, "T1" );
connectionAB.setProperty( "departure", "11:00" );
connectionAB.setProperty( "arrival", "11:45" );
Relationship connectionBC = connectStations( stationB, stationC, "T1" );
connectionBC.setProperty( "departure", "11:50" );
connectionBC.setProperty( "arrival", "12:30" );
Relationship connectionCD1 = connectStations( stationC, stationD, "T1" );
connectionCD1.setProperty( "departure", "12:35" );
connectionCD1.setProperty( "arrival", "13:00" );
Relationship connectionCD2 = connectStations( stationC, stationD, "T2" );
connectionCD2.setProperty( "departure", "14:35" );
connectionCD2.setProperty( "arrival", "15:00" );
Relationship connectionAE = connectStations( stationA, stationE, "T2" );
connectionAE.setProperty( "departure", "13:15" );
connectionAE.setProperty( "arrival", "13:45" );
Relationship connectionEC = connectStations( stationE, stationC, "T2" );
connectionEC.setProperty( "departure", "13:50" );
connectionEC.setProperty( "arrival", "14:30" );
(5)
for ( Relationship connection : stationA.getRelationships(
MyRelationshipTypes.CONNECTION ) )
{
System.out.println( "Train " + connection.getProperty( "path" ) +
": departure " + connection.getProperty( "departure" ) );
}
(6)
You'll have to do this with a traverser and custom evaluators (See f.ex.
http://wiki.neo4j.org/content/Design_Guide#Searching_using_traversing)
public class PathEvaluator implements StopEvaluator
{
private final String pathName;
public PathEvaluator( String pathName )
{
this.pathName = pathName;
}
public boolean isStopNode( TraversalPosition position )
{
// Do we have an outgoing connection for the given path?
for ( Relationship connection :
position.currentNode().getRelationships(
MyRelationshipTypes.CONNECTION, Direction.OUTGOING ) )
{
if ( connection.getProperty( "path" ).equals( pathName ) )
{
// We do, then this is NOT a stop node, i.e. go on
return false;
}
}
return true;
}
}
for ( Node station : stationA.traverse( Traverser.Order.DEPTH_FIRST,
new PathEvaluator( "T1" ), ReturnableEvaluator.ALL,
MyRelationshipTypes.CONNECTION, Direction.OUTGOING ) )
{
// Print information. You don't get the relationships from the
traverser, but
// you can either write a custom ReturnableEvaluator or find the wanted
// relationship from the station node and get the one with the
property "path"="T1".
}
In addition to this you'd probably want to index your station nodes
(see http://components.neo4j.org/index-util/) and it's generally a
good idea to connect all your station nodes to a "station reference
node" so that you can iterate through all of them if you'd like to
(http://wiki.neo4j.org/content/Design_Guide#Organizing_your_Nodespace).
Then you'll have to wrap your operations in a transaction
(http://wiki.neo4j.org/content/Design_Guide#Transaction_handling) and
call neo.shutdown() before the JVM halts.
This was just a very basic example of how your application could look
like. The one thing that doesn't really work in a bigger example is
the departure/arrival times which sits on the connections, it can be
solved in many other ways. Don't hesitate to ask for help if you get
stuck trying to come up with a good solution to that problem.
Have fun with this application!
/ Mattias
2009/6/28, Bert Fitié <b...@analytag.com>:
>
> Hi,
>
> I'm new to the list and Neo4j (and my Java is rather rusty). I want to
> investigate the easy-of-use of Neo4j for a (large) railway network
> application.
>
> (1) Nodes. The nodes of this network are railway stations.
> (2) Relationships. There is only one (directed) RelationshipType (ARC)
> between stations.
> (3) Paths. There are named paths (e.g. trains). A path P consists of a
> sequence of arcs that all have a property named "P". The value of this
> property could be a distance between two stations or a departure and
> arrival time and will (usually) be different for each arc.
> (4) Usage. The application will be used for the following navigation.
> (4.1) The user selects a start station.
> (4.2) A list will be generated of all outgoing paths from this
> station.
> (4.3) The user selects a path (e.g. a train)
> (4.4) A sequence will be generated of all stations on this path
> (4.5) The user selects a station from the path
> (4.6) If this station is the final destination, the user is done,
> otherwise, the user returns to (4.2)
>
>
> Could you provide me with (guidelines for) Neo4j code for the
> following example network:
>
> (1) The example network has 5 nodes (stations): A, B, C, D, E
> (2) The example network has 5 arcs: AB, BC, CD, AE, EC
> (3) The example network has 2 paths (trains): T1, T2
> (4) The example network has 6 arc (path) properties:
> (4.1) AB: "T1" => "departure=11:00 arrival=11:45"
> (4.2) BC: "T1" => "departure=11:50 arrival=12:30"
> (4.3) CD: "T1" => "departure=12:35 arrival=13:00"
> (4.4) CD: "T2" => "departure=14:35 arrival=15:00"
> (4.5) AE: "T2" => "departure=13:15 arrival=13:45"
> (4.6) EC: "T2" => "departure=13:50 arrival=14:30"
> (5) Traversal 1: given station A, give a list of all outgoing paths
> from this station.
> Result:
> * Station A
> - Train T1: departure 11:00
> - Train T2: departure 13:15
> (6) Traversal 2: given an outgoing path from a station, give the
> sequence of stations on this path.
> Result in case of selecting T1:
> * Train T1
> - Station A, departure 11:00
> - Station B: arrival 11:45, departure 11:50
> - Station C: arrival 12:30, departure 12:35
> - Station D: arrival 13:00
> Result in case of selecting T2:
> * Train T2
> - Station A, departure 13:15
> - Station E: arrival 13:45, departure 13:50
> - Station C: arrival 14:30, departure 14:35
> - Station D: arrival 15:00
>
>
> Your help is very much appreciated!
>
> -- Bert Fitié
>
> _______________________________________________
> Neo mailing list
> User@lists.neo4j.org
> https://lists.neo4j.org/mailman/listinfo/user
>
--
Mattias Persson, [matt...@neotechnology.com]
Neo Technology, www.neotechnology.com
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