Hey Aaron,
A Port typically has two uni-directional links to another device, and two uni-directional crossconnects (crossconnects are also links). So then it has two source relations and two sink relations.
Is a cross-connect a subclass of link?
These are open issues. I assume that you're asking for Freek and Jeroen's opinion here, or maybe the output of the discussion. In my opinion, cross-connect is a specific type of link. Whether that is manifested as a subclass depends on whether their are structural differences in their descriptions that cause them to require different objects rather than different roles of the same object.
Freek also brought up an example where a SONET switch with an Ethernet interface. If you just look at the Ethernet Layer, this would appear as a Port with links ("actual link links") to two devices.
What two devices does it have an actual link to? Maybe i'm being dense?
I might be being dense as well, but I think this case refers to a port connecting on the internal side to a cross-connect (or the backplane) and a regular link on the outside. best, martin