[Standards-JIG] Question on PubSub leased subscriptions

Jean-Louis Seguineau jean-louis.seguineau at laposte.net
Thu Feb 2 08:56:40 UTC 2006


As no-one has taken to answer my previous post, I will reformulate the
question. The 12.12 Implementing Time-Based Subscriptions (Leases) section
describes how leased subscriptions should be handled. In itself this section
allow much freedom to the implementers.

The section properly describe how one can specify a TTL associated with a
particular subscription, and how to refresh the TTL value in due time. But
the section fail short in describing how the subscription expiration event
should be conveyed back to the subscriber. 

The deterministic nature of XMPP and the preference for 'complex servers and
simple client' requires that changes in states are properly conveyed to
subscribers. And lease expiration is an important change of state.

Question remain on how to indicate the lease expiration in the event
message. Trying to remain consitent with the JEP, can we envisage something
like:

<message from='pubsub.shakespeare.lit' to='francisco at denmark.lit' id='foo'>
  <event xmlns='http://jabber.org/protocol/pubsub#event'/>
  <headers xmlns='http://jabber.org/protocol/shim'>
    <header name='pubsub#subid'>123-abc</header>
    <header name='pubsub#expired'>2006-02-02T02:56:15Z</header>
  </headers>
</message>

The only required changes are the inclusion of the example in the 12.12
section and the addition of a SHIM header definition.

Jean-Louis

-----Original Message-----
From: Jean-Louis Seguineau [mailto:jean-louis.seguineau at laposte.net] 
Sent: Friday, January 13, 2006 8:14 PM
To: 'standards-jig at jabber.org'
Subject: PubSub leased subscriptions


While we are revising the jep-60, I would like to get the experts answer on
lease based subscriptions. There is a mention of optional
leased-subscription support that can be implemented by a pubsub service. The
way to specify a lease time is quickly described in 12.12.

What would be the correct way to notify the subscription lease's expiration?

I suppose that according to the JEP we would send a notification <message>
with probably the last known published state, but how would we declare the
fact that the subscription has actually expired? What construct would we
use?

Jean-Louis





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