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RE: WSDL and pub/sub

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Thu, 12 Feb 2004 10:34:44 -0800
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9039589BE@MAIL01.stc.com>
To: "Burdett, David" <david.burdett@commerceone.com>, "Steve Ross-Talbot" <steve@enigmatec.net>, "WS Choreography" <public-ws-chor@w3.org>
Does it make sense for us to define the details of a pub/sub mechanism
(e.g. the delivery address representation) when there are already specs
like WS-Eventing and WS-Notification which do that?
 
Ugo

	-----Original Message-----
	From: public-ws-chor-request@w3.org
[mailto:public-ws-chor-request@w3.org] On Behalf Of Burdett, David
	Sent: Thursday, February 12, 2004 10:23 AM
	To: 'Steve Ross-Talbot'; WS Choreography
	Subject: RE: WSDL and pub/sub
	
	

	Steve 

	Giving this a bit of thought makes me think that the essence of
pub-sub is ... 

	1. The publisher sets up a service that accepts subscriptions
requests and changes for some other service that actually publishes
documents/messages.

	2. The subscriber then requests subscription to a service by
sending a messge which then gets either accepted or rejected.

	3. When the subscriber makes the request, they must include some
kind of "delivery address" that identifies where documents/messages etc,
generated by the publisher must be sent

	4. If the request is accepted, then the publisher will return
some kind of "identifier" for the subscription that can later be used
when changing or cancelling the subscription

	5. The publisher starts publishing documents. This is a one-way
message although it might be delivered reliably 
	6. The publisher continues publishing documents until: a) the
subscription is cancelled, or b) the subscription runs-out, e.g. a
certain period of time has passed, a specific number of
messages/documents have been received, the subscriber hasn't paid.

	From a CDL perspective, the "delivery address" is what the
Overview Model calls a "Channel". This means that to use it, we need to
have a way of representing the Channel in XML and decie how it should be
included in the message. My thoughts would be the body.

	The rest sounds to me like a pretty regular Choreography
Definition with dependencies, e.g. you can't cancel a subscription
unless you managed to subscribe to it successfully.

	Another question is should such a Pub-Sub Choreography be
standardized as I am sure the need for Pub-Sub goes beyond WS Chor. For
example you could imagine a definition that allowed you to manage a
subscription to any web service then later cancel it. However you would
need standard XML docs to be used as Message Content for the
Interactions in the Pub Sub.

	Also where should such a spec be developed ... by WSDL, by WS
Chor? I'm not sure I know the answer to that one. 

	David 



	-----Original Message----- 
	From: Steve Ross-Talbot [mailto:steve@enigmatec.net] 
	Sent: Thursday, February 12, 2004 5:41 AM 
	To: WS Choreography 
	Subject: Fwd: WSDL and pub/sub 



	How does this leave our stuff wrt the Barros usecase? 

	Cheers 

	Steve T 


	Begin forwarded message: 

	> From: "Jonathan Marsh" <jmarsh@microsoft.com> 
	> Date: 11 February 2004 20:44:41 GMT 
	> To: "Steve Ross-Talbot" <steve@enigmatec.net> 
	> Subject: RE: WSDL and pub/sub 
	> 
	> WSDL 2.0 part 3 [1] describes some message exchange patterns
that can  
	> be 
	> used as part of a pub/sub solution.  Look at all the "out-*"
patterns 
	> starting at section 3.4.  A complete pub/sub solution is not
provided, 
	> as the address and mechanics of "sub"ing and providing the
address for 
	> the "pub" to be delivered are not standardized in WSDL
(perhaps this is 
	> an orchestration problem?).  Note that the HTTP and SOAP
bindings don't 
	> support these message exchange patterns yet, but we have an
issue open 
	> on whether we should rectify this. 
	> 
	> Hope this helps. 
	> 
	> [1] 
	>
http://dev.w3.org/cvsweb/~checkout~/2002/ws/desc/wsdl20/wsdl20- 
	> patterns. 
	> html#out-only 
	> 
	>> -----Original Message----- 
	>> From: Steve Ross-Talbot [mailto:steve@enigmatec.net] 
	>> Sent: Tuesday, February 10, 2004 10:07 AM 
	>> To: Jonathan Marsh 
	>> Subject: WSDL and pub/sub 
	>> 
	>> Jonathan, 
	>> 
	>> I seem to recollect that you indiciated that WSDL2.0 includes
an MEP 
	> or 
	>> some such facility to represent pub/sub as a means of
communication. 
	>> Could you verify this? And could you point me to the
appropriate 
	>> description? This is something that the Choreography WG would
very 
	> much 
	>>   like to have so that a single message could be sent to
multiple 
	>> sources without needing to bind to those sources. 
	>> 
	>> 
	>> Best Regards 
	>> 
	>> Steve Ross-Talbot 
	>> co-Chair W3C Web Services Choreography 
	>> 
	>> O: +44 207 397 8207 
	>> C: +44 7855 268 848 
	>> www.enigmatec.net 
Received on Thursday, 12 February 2004 13:34:45 GMT

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