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RE: WSDL and pub/sub

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Thu, 12 Feb 2004 12:14:00 -0800
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9032B8A46@MAIL01.stc.com>
To: "Martin Chapman" <martin.chapman@oracle.com>, "Burdett, David" <david.burdett@commerceone.com>, "Steve Ross-Talbot" <steve@enigmatec.net>, "WS Choreography" <public-ws-chor@w3.org>
Great, so we would have to deal with three pub/sub specs instead of only
two ;-) 
Convincing the proponents of existing pub/sub specs to give them to a
standards organization seems to be a somewhat less painful path.
 
Ugo

	-----Original Message-----
	From: Martin Chapman [mailto:martin.chapman@oracle.com] 
	Sent: Thursday, February 12, 2004 12:02 PM
	To: Ugo Corda; 'Burdett, David'; 'Steve Ross-Talbot'; 'WS
Choreography'
	Subject: RE: WSDL and pub/sub
	
	
	we could of course define some open standards in this space :-) 

		-----Original Message-----
		From: public-ws-chor-request@w3.org
[mailto:public-ws-chor-request@w3.org] On Behalf Of Ugo Corda
		Sent: Thursday, February 12, 2004 6:35 PM
		To: Burdett, David; Steve Ross-Talbot; WS Choreography
		Subject: RE: WSDL and pub/sub
		
		
		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 15:14:01 GMT

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