Re: [wsn] "despite some wording in the introduction"

[Peter Niblett <peter_niblett@uk.ibm.com>]

David

I suggest that the issue be called "Indirect Notification Pattern", and
that it goes in chapter 1 of the issues list - i.e. WSN 1.6, but as you
point out it also has a bearing on BaseNotification.

How about...

WSN:1.6 Indirect Notification Pattern

The WS-Notification specifications call out two distict notification
patterns,

1. "direct notification"  where a subscriber places a subscribe request
against a specific NotificationProducer, and the NotificationProducer
delivers notfication messages to the nomininated NotificationConsumer

2. "brokered notification" where a subscriber places a subscribe request
against a NotificationBroker, and the NotificationBroker forwards
notification messages to the nominated NotificationConsumer; these
notification messages originate from other source(s).

However there is a third pattern:

3."indirect notification", This third pattern combines elements of the
previous two. A subscriber places a subscribe request against a specific
NotificationProducer and that NotificationProducer delegates the job of
delivering the Notification messages to the nominated NotificationConsumer
(and possibly managing the subscriptions) to another intermediary service.

This issue states that this third pattern should be explicitly called out
as valid, and that any wording in the various specifications that states
that it is invalid should be corrected.

Specifications

-  WS-Notification whitepaper
-  WS-BaseNotification

Peter Niblett
IBM Senior Technical Staff Member




                                                                           
             David Hull                                                    
             <dmh@tibco.com>                                               
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             18/06/2004 21:56          wsn@lists.oasis-open.org            
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                                                                   Subject 
                                       [wsn] "despite some wording in the  
                                       introduction"                       
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Lines 105-110 of the 17 June draft read:


      The NotificationProducer maintains a list of subscriptions (each
      subscription entry contains the Topic(s), a reference to the
      NotificationConsumer and possibly additional information). When it
      has a notification to distribute, the NotificationProducer matches
      the notification against the interest registered in each Subscription
      known to it. If it identifies a match it issues the Notification to
      the NotificationConsumer associated with that Subscription.


First, technically the NotificationProducer would maintain a set of
subscriptions, not a list (list implies ordering and allows duplication,
set is unordered and without duplication, albeit subscriptions can be
identical in everything but their unique ID).

More importantly, my understanding is that the interactions defined in WSBN
are common to all delivery methods, whether direct, brokered, gatewayed or
whatever else.  If I want to make a subscription, I subscribe, and it's up
to the rest of the system to decide how the notifications reach the
consumer.

Similarly, lines 114-117 strongly imply that WSBN covers only the direct
scenario, and that direct and brokered are the only games in town:
      The configuration where a NotificationConsumer is subscribed directly
      to the NotificationProducer is referred to as the “direct” or
      “point-to-point” notification pattern. There are other variations of
      the Notification pattern, where the NotificationConsumer is
      subscribed to an intermediary NotificationBroker service. These are
      covered by the [WS-Brokered Notification] specification.
I would propose to strike 114-117 entirely, and replace the passage from
105-110 with "The NotificationProducer arranges for the proper
notifications to reach the NotificationConsumer, whether by notifying the
NotificationConsumer directly or by delegating to some other facility."