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RE: Definition of Choreography

From: VAMBENEPE,WILLIAM (HP-Cupertino,ex1) <william_vambenepe@hp.com>
Date: Fri, 18 Oct 2002 17:45:49 -0700
Message-ID: <155C6BB395577C4EA8F65A9ADA9F2104DA8C12@xcup01.cup.hp.com>
To: www-ws-arch@w3.org

An illustration of the "public process" that David describes can be found in
the WSCL (Web Services Conversation Language) W3C note. To reuse David's
words, WSCL "[constrains] what a private process can do when interacting
with services outside of its direct control."

WSCL note: http://www.w3.org/TR/wscl10/



William Vambenepe
Web Services Management Operation
HP OpenView Division

> -----Original Message-----
> From: Burdett, David [mailto:david.burdett@commerceone.com]
> Sent: Friday, October 18, 2002 4:58 PM
> To: 'Champion, Mike'; www-ws-arch@w3.org
> Subject: RE: Definition of Choreography
> Mike
> Some observations on WSCI, BPEL4WS and choreographies.
> Having reviewed WSCI and BPEL4WS, they both tend to focus on 
> how to sequence
> processes to carry out a particular activity. As such they 
> tend to focus on
> "private" processes within the enterprise.
> What I don't think they do so well, is describe the public 
> processes, often
> described as choreograhpies, that **constrain** what a 
> private process can
> do when interacting with services outside of its direct control.
> I think this is an important distinction as:
> 1. Public processes need to be standardized, private ones do not.
> 2. Anything that needs to be standardized should have a 
> formal way of being
> defined as an aid to understanding and therefore interoperability
> You also need to distinguish between the generic implementation of a
> standardized process/choreography and an individual actual 
> implementation.
> A generic choreography definition just needs to say, for 
> example, ... "if
> you send me an "order" then you must send me an "order 
> response" back - and
> really nothing more".
> I could have said, but didn't ... "if you send me a RosettaNet Order
> contained as an PKCS7 encrypted attachment on a "SOAP with 
> attachments"
> message to this URL using HTTP, then I will send you a 
> RosettaNet Order
> Response in the same format to the URL you specify in return".
> It's all to do with layering. The generic choreography is a universal
> business pattern that is independent of how it is implemented, and
> specifically the service that implements it. If the only way 
> you can define
> a choreography is as part of defining an actual instance then 
> you will get
> unnecessary **massive** duplication of choreography definitions.
> David
> -----Original Message-----
> From: Champion, Mike [mailto:Mike.Champion@softwareag-usa.com]
> Sent: Friday, October 18, 2002 3:12 PM
> To: www-ws-arch@w3.org
> Subject: RE: Definition of Choreography
> > -----Original Message-----
> > From: Mark Baker [mailto:distobj@acm.org]
> > Sent: Friday, October 18, 2002 3:45 PM
> > To: Cutler, Roger (RogerCutler)
> > Cc: 'Dave Hollander'; Burdett, David; 'Mark Baker'; Champion, Mike;
> > www-ws-arch@w3.org
> > Subject: Re: Definition of Choreography
> > 
> > 
> > Another +1 from me.  Let's see some use cases that 
> > demonstrate why it's important to expose choreographies.  
> > Because as we've seen from these
> > specs, they're not exactly simple, and if you can 
> accomplish something
> > without needing to agreeing to new stuff, that reduces coordination
> > costs (read; reduces cost of doing business).
> I really, really hope we can stay focussed on identifying the 
> components,
> connectors, and data that are identified by the BPEL4WS and 
> WSCI specs,
> determine which of these are important to cover in a 
> Choregraphy spec, and
> write this up in a way that makes a good case to the W3C AC 
> for chartering a
> WG to define such a spec.  That's what we've agreed to do at 
> the F2F and in
> response to the request for a tighter scope by the WS CG.  
> Use cases would
> definitely help in that effort, and I think the "Definition 
> of Choreography"
> thread has gotten some ideas going.
> A "devil's advocate" position that this isn't needed is very useful in
> sharpening our arguments, and Mark does SUCH a good job at it 
> :-)  Still,
> let's not get too distracted by arguing for or against the idea that a
> Choreography spec is needed -- we already decided that it is! 
> -- and focus
> on defining what exactly the scope of a Choreography WG would 
> be.  When we
> have a better handle on that, getting pushback helps us make 
> the case, and
> gets the counter-arguments on the record for the AC's use.
> To put it another way, I'll feel that we've done our job if 
> we analyze WSCI
> and BPEL from the WSA framework, make the best case for a new 
> WG, but the AC
> disagrees.  I will NOT feel that we've done our job if we 
> spend the next
> month arguing about whether to do the analysis or not and 
> then offer nothing
> to help the AC make their decision.
Received on Friday, 18 October 2002 20:46:46 UTC

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