Subject: Re: Re: AW: [Simple] reachibility information for services in current presence data model

From: "Hyttfors, Per" <[email-masked]>
Date: Wed, 6 Apr 2005 12:39:55 +0200

Hello,

Lets say that the same person would have several devices with the same
service running on all of them (lets say a telephone service) but with
different service contact addresses (telephone numbers). Each device
will have its own Presence User Agent that publish its part of the
presence information. Would this scenario require that the NOTIFY that
is sent to a watcher with the overall presence information of that
person would have to contain several <tuples> with different contact
addresses but with the same duplicated service information? (in the case
that the service is the exact same one for all devices)

/Per

Henning Schulzrinne wrote:
>Unless there is some significant difference between services, you 
>wouldn't publish multiple contact addresses for it. Thus
>
><tuple>
>    ... description ...
>    sip:foo@somewhere
>    sip:bar@example
>    sip:123@whoknows
></tuple>
>
>makes very little sense - why publish three URIs that the observer has 
>no way of distinguishing? If there's no annotation, the user can only 
>throw darts and pick one.
>
>With the possible exception of having both a "tel" and SIP URI that 
>reach the same device, I see little practical use for your description,

>but maybe I'm misunderstanding your use case.
>
>Boehmer Bernhard Com Berlin wrote:
>> Hi Henning,
>> my assumption is that a user has a certain service available
>> at different locations (devices, agents, etc.) each identified
>> by different contact addresses. The user wants to publish all
>> these contact addresses for this service. Together with the contact
>> information, however, (s)he also publishes also a bunch of other
>> information about this service. Due to the fact that only one contact
>> is possible in <tuple>, my current understanding is that the user has
to publish
>> multiple tuples indicating the different contacts but *duplicating*
>> the other service information. This information, therefore, seems to 
>> be doubled. I would like to avoid this redundancy somehow.
>>

Per Hyttfors 
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---

From: Paul Kyzivat <[email-masked]>
Date: Wed, 06 Apr 2005 10:32:20 -0400

> that the service is the exact same one for all devices)

This is a function of how the multiple sources of presence information 
are composed by the presence server. Simply making a union of all the 
tuples (which is what you ask about) is one simple approach, because it 
requires no understanding on the part of the part of the presence 
server. But it is clear that people would like to have more intelligent 
composition policies. So far we have deferred actually defining such 
intelligent composition policies just because it is hard and we want to 
get something out. But it is entirely permissible to implement such a 
compostion policy even in the absence of a standard.

	Paul