Re: proposal for 7478

This response concerns point 2) and 3) in the proposal as point 1) is in
a separate issue and point 4) depends on 2) and 3).

This proposal changes the current WS-E draft in the following ways:

1) It removes the possibility for an event source to return an
expiration that is less/earlier than the value requested by the
subscriber in a successful subscription;

2) It removes the following paragraph from the definition of Expires
element in Section 4.1:

If this element does not appear, then the request is for a subscription
that will not expire. That is, the subscriber is requesting the event
source to create a subscription with an indefinite lifetime. If the
event source grants such a subscription, it MAY be terminated by the
subscriber using an Unsubscribe request, or it MAY be terminated by the
event source at any time for reasons such as connection termination,
resource constraints, or system shut-down. 

By change 1), it assumes all subscribers will never accept any
subscriptions with a shorter expiration. Therefore, there is no need to
create such subscription in the first place. While this may be the case
in some situations, I'm not sure WS-E should enforce this assumption for
all situations. In some situations, a subscriber may want to accept a
subscription with a shorter expiration, with the hope that it can renew
it later on when the event source is less loaded. In some cases, getting
some notifications now is better than getting no notifications at all.
If we remove this flexibility, a subscriber desperate for notifications
has to repeatedly submit subscriptions with shorter expiration in order
to be accepted. Therefore, I feel this restriction should be enforced by
the event source implementations, instead of the spec itself. 

By change 2), the proposal gives the people impression that an
indefinite subscription cannot be terminated by the event source. 

Thanks,

Li Li

Received on Wednesday, 16 September 2009 14:20:37 UTC