Subject: [Simple] draft-ietf-simple-event-list: identifying list subscriptions

From: <[email-masked]>
Date: Mon, 24 Apr 2006 12:25:53 +0200

Hello, 

As mentioned in the draft, SIP URI does not indicate whether it belongs
to list of resources or to single resource. Can I assume that Supported:
eventlist header means that the subscription is a list subscription, or
can it happen that also subscription to single resource contains
Supported: eventlist? This differentiation is needed if the server
handles both subscriptions to list and subscriptions to single resources
...

Thank you, 

Silvestr Peknik
Software Specialist
TietoEnator

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From: Adam Roach <[email-masked]>
Date: Mon, 24 Apr 2006 12:15:37 -0500

[email-masked] wrote:
> Supported: eventlist?

The "Supported: eventlist" header field in the request simply means that
the client *understands* list subscriptions. It has no implication
regarding whether the client expects the indicated resource to be a list
or not.

So, the statement is even stronger than you put it: it's not just that a
subscription to a single resource *CAN* contain "Supported: eventlist"
-- it's that it *MUST* contain "Supported: eventlist" if the subscriber
understands the event list format. (I'm using this "must" as a "this is
the only way, in my opinion, a reasonable implementation can behave,"
not as a standards statement. The specification would technically allow
the client to pick and choose which subscriptions to indicate event list
support -- but not indicating support for event lists would always make
things work worse, and never better).

> This differentiation is needed if the server

No, it's not.

It *is* true that the server needs to know whether a subscription is to
be treated as a list subscription or as a subscription to a single resource.

This is exactly the same statement that a terminating MTA needs to know
whether an email message is intended for a single account or for a
mailing list.

In both cases, the server knows this *independent* of what the client
sends. The server knows whether it's a single resource or whether it's a
list because it's *provisioned* to know which URIs (or email addresses)
correspond to single resources and which URIs (or email addresses)
correspond to lists.

/a