[Nml-wg] Serial compound relations: "last" call on concepts, part 1

[Freek Dijkstra]

Hi,

At the previous call I was assigned the following work item (someone my
absence from the call put me on the "I volunteer" list; at least that's
what I was told afterwards :~O )

> * Serial Compound Relations Syntax
> Freek put this on the agenda to close our discussion we had on the
> mailinglist. We had a too small group to make a decision on this.
> It would also help if we had a summary of the discussion until right
> now. Freek, could you provide that?

I have not caught up with all yet, but like some sort of workgroup last
call for the following decision:

There are three ways to describe a serial compound relation (thus the
segmentation of a end-to-end link on a single layer)

1. It should be possible to say that a link A is a segment of another
link E.
2. It should be possible to say that a link A has sink port X, and port
link has source port X, meaning that link A is directly connected to link B.
3. It should be possible to say that a link A is followed by the "next"
link B.
4. It is possible to say that a link A is the "first" link (segment) of
a link E (the end-to-end link), and it is possible to say that a link D
is the "last" link (segment) of a link E.
5. We only use the concept of "links", not of "segments" or "end-to-end
link", it is the _relation_ that determine if some link is a "segment"
of another link or not.

(Note that this explicitly chooses the "first", "next", "last" relations
as proposed by Aaron, not the numbered (1,2,3,...) relations as proposed
by Freek.)

With the following additions:

Ad 2. In case 2, links that are cross connects within a device MUST be
listed.
Ad 3. In case 3, cross-connect links MAY/MUST(?) be skipped, meaning
that in the situation:
 - sink of link A is port X
 - source of link C is port X
 - link C is of type "crossconnect"
 - sink of link C is port Y
 - source of link B is port Y
then one can (MUST? MAY?) say that:
 - the "next" link following link A is link B
instead of:
 - the "next" link following link A is link C (of type crossconnect)
 - the "next" link following link C is link B

There is more to say on this topic (e.g. the above does not discuss
syntax in any way), but the above is what I have seen in proposals and
examples. I now like to ratify or reject this by the working group.

Please mail your comment (even if it is just "OK") within three weeks.
We particular like input on addendum 3. (is that a "MAY" or a "MUST"?)

Thanks,
Freek