[Nml-wg] Adaptations (was: More UML....)

[Freek Dijkstra]

John Vollbrecht wrote:

> So what exactly is an adaptation.

See also my mail yesterday.

Loosly, adaptation is the encapsulation of one data layer into another 
data layer.

A de-adaptation is the extraction of data from that lower layer (which 
also terminates the lower layer path).

Formally (G.800):
> The adaptation source function is a labelling and encoding entity that takes one or more client 
> communications passing through its client facing input port(s), and combines them into instances of 
> adapted information. The adaptation source function also adds sufficient labelling in order to 
> distinguish each client communication from all others within the scope of the access point to which 
> the adaptation source is bound. The instances of adapted information are passed through the server 
> facing port. 



> For example, and OTN port might  
> convert things to SONET, Ethernet, and other line protocols.  Is this  
> adaptation?

Yes, if "things" is a higher layer than SONET or Ethernet.

> Also, what is it that keeps there to be only two adaptations?

There is at most one adaptation per data source: that data is adapted 
into one or more server layer channels using ONE adaptation function.
However, our ports are bidirectional, and thus have two sources and two 
sinks. Therefore, a port can have at most two adaptations.

The same applies for links and cross connects: since there are two 
sources and two sinks per port, there can be two links and/or two cross 
connects at most. (Typically, one link and one cross connect, but I know 
of situations with two links)

It is still open for discussion if this is the best approach. Thinking 
of it now, I am almost inclined to define unidirectional ports, though I 
think that is too verbose for most topology descriptions.

>> Another point that I was thinking about: what is the cardinality of  
>> the implementedBy relation? I think it might be *-*, but I'm not sure.

I'd say 1:*, since one (virtual) node is -I think- typically implemented 
by a physical node.

The converse, a set of nodes behaving like a virtual node is handled by 
the topology concept (formerly known as Graph, formerly know as Network)


Regards,
Freek