I vote for option 3, it makes the most sense to me. Guy -----Original Message----- From: Freek Dijkstra [mailto:Freek.Dijkstra@sara.nl] Sent: 07 August 2009 14:05 To: Network Markup Language Working Group Subject: [Nml-wg] Transitivity of hasPort Freek Dijkstra wrote (in "Use case: cross connect (single layer)"):
Here is the use case of the cross connect (single layer).
Paola Grosso wrote:
- Transitivity of relation, such as if a device is at one Location, all its Ports are at the same location. Should transitivity specified in the model or implicit?
The problem I had is there there were 16 "hasPort" relations for 8 unidirectional ports: a hasPort relation between the Node and each port, and a hasPort relation between the SwitchMatrix Service and each port. In the call I wondered if this can be an implicit relation. I recently thought about this, and it seems we have 3 options: 1) No transitivity: You have to specify all 16 "hasPort" relation, as in the example I sent out previous week. 2) Transitivity from Node to Service: If there is a hasPort relation between a Node and a Port, and also a hasService between the same Node and a Service, then it is implied that there is also a hasPort relation between the Service and the Port, _provided that the Port is on the same layer as the Service_. This scenario was discussed in the call, and we added this condition to cope with Nodes with services on multiple layers. 3) Transitivity from Service to Node: If there is a hasPort relation between a Service and a Port, and also a hasService between a Node and the same Service, then it is implied that there is also a hasPort relation between the Node and the Port. This last scenario was not discussed, but I think it makes more sense: this way we would not need the additional condition that the Port is on the same layer as the Service. Less conditions = better. Regards, Freek _______________________________________________ nml-wg mailing list nml-wg@ogf.org http://www.ogf.org/mailman/listinfo/nml-wg