Subject: [SIMPLE] PState (Publication-State) Header

From: Tan Ya-Ching ICM N PG U ID A 1 <[email-masked]>
Date: Thu, 27 Jun 2002 17:01:17 +0200

draft-olson-simple-publish-00.txt introduced the PState header. It is stated
that "The response to the PUBLISH MUST contain the Publication-State header
in order to provide the publisher the duration for which the publication is
considered valid. The value of this may be decreased from the expiration
given by the publisher in the original PUBLISH method, but SHOULD NOT be
increased".

I have some questions:

- If the expiration value in the response is mandatory and it depends on the
expiration given by the publisher, shouldn't it be mandatory for the
publisher to give a value in PUBLISH ? The draft only states the "the
PUBLISH may contain an expiration value". Another way is to specify in the
draft a default expiration value in the absence of the Expires header in
PUBLISH.

- Why can't the Expires header be used instead of adding a new header PState
?

- If the event state that is published through the PUBLISH method is
soft-state, where would the expiration timer be running and what happens
when it expires? Does the presence agent send a notification to the watchers
when it happens and if yes, what should the state be changed to ?

Regards,
Ya-Ching

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---

From: "Sean Olson" <[email-masked]>
Date: Thu, 27 Jun 2002 08:34:03 -0700

Some answers inline below.
Thanks for the quick comments!
/sean

-----Original Message-----
From: Tan Ya-Ching ICM N PG U ID A 1
[mailto:[email-masked]] 
Sent: Thursday, June 27, 2002 8:01 AM
To: [email-masked]'; Sean Olson
Cc: [email-masked]
Subject: [SIMPLE] PState (Publication-State) Header

draft-olson-simple-publish-00.txt introduced the PState header. It is
stated that "The response to the PUBLISH MUST contain the
Publication-State header in order to provide the publisher the duration
for which the publication is considered valid. The value of this may be
decreased from the expiration given by the publisher in the original
PUBLISH method, but SHOULD NOT be increased".

I have some questions:

- If the expiration value in the response is mandatory and it depends on
the expiration given by the publisher, shouldn't it be mandatory for the
publisher to give a value in PUBLISH ? The draft only states the "the
PUBLISH may contain an expiration value". Another way is to specify in
the draft a default expiration value in the absence of the Expires
header in PUBLISH.

[Sean] I don't believe it should be mandatory for the publisher. It is
mandatory in the response to make it clear
       that this is soft-state. The publisher, however, may have no
prior notion of how long the publication state
       is valid for -- it may even be indefinite.

- Why can't the Expires header be used instead of adding a new header
PState ?

[Sean] The reasoning is that we should avoid using Expires: in the same
manner as REGISTER. But this is a
       valid question and Jonathan has pointed out that Expires: would
be a more appropriate header as well.
       I'm open to changing this in the -01 version of this draft.

- If the event state that is published through the PUBLISH method is
soft-state, where would the expiration timer be running and what happens
when it expires? Does the presence agent send a notification to the
watchers when it happens and if yes, what should the state be changed to
?

[Sean] The expiration timer would be running in the presence agent in
our model. When the timer expires, the state
       is purged, and a notification should be generated. The state
would be changed to the composite state resulting
       from the removal of this slot (i.e. the compositor should be
involved to determine the new composite state).
       This should be more clearly spelled out and will be included in a
-01 draft.

Regards,
Ya-Ching