Hi Jerry and others, Looking at your slide, I see two concepts, and I'm not sure if they're the same or not. The first concept is the hierarchical topology: describing a topology in more and more (or less and less) detail. The second concept is the alias: using a pointer to point from a generic port or link ("the link between Nordunet and MAN LAN") to a more concrete network element ("the link between Ciena 4000, intf 2/1 in CPH001a and the Foundry 1234 intf 8/0 in NY002a"). Both concepts seem to deal with abstraction and can help distinguishing between a _functional description_ of a network, and how those function are _implemented_. However, the first concept is mostly about aggregation, while the second is about versioning. While I see aggregation as some "geographic" thing (how far do you zoom in area), the version is a "time" thing (from when to when is this conceptual link in place, and when is it ported to a different device). I think NML can support either concept, but I wonder if we should support both concepts, or if supporting one is good enough, or perhaps both concepts are the same after all. Regards, Freek