Re: [Simple] Re: Presence Data Model: Overriding services (tuples)

[Paul Kyzivat <pkyzivat at cisco.com>]

Henning Schulzrinne wrote:
> > Out of curiosity, is there anything that says that the contact uri must
> > be unique within the composed document? With the service tuples being
> > identified by tuple-id:s, is there anything preventing to such tuples
> > having the same contact uri:s?

At the moment the answer is that Jonathan's data model document says 
they must be unique.

> There are several plausible scenarios where you could have the same 
> contact URI appear twice. For example, limitations in the capabilities 
> description may not allow you to express "this URI can do A1,A2,A3  OR 
> it can do B1,B2,B3" (but not random combinations of sub-capabilities 
> such as A1,B1).

I am torn about this. I fully agree with this example, and repeating the 
contact address in two tuples seems the most straightforward way to 
represent it.

OTOH, I agree that there are benefits to having the addresses be unique. 
Specifically, its hard to imagine how a composition policy could work if 
two tuples with the same contact could represent *either* an override or 
two services available simultaneously at the same address.

I don't know if this can be resolved without first tackling the problem 
of composition policy. But I think that will be a long time in coming.

I guess my inclination is to *allow* duplicates for now, and leave it as 
a later exercise to possibly restrict them as part of a composition 
policy. I don't think the presence of duplicates should be a problem for 
watchers.

	Paul


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