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RE: multiple partners in CDL

From: Barros, Alistair <alistair.barros@sap.com>
Date: Mon, 18 Oct 2004 13:49:35 +0200
Message-ID: <A54EC476B74FD31186340008C791CBD0104E66F1@ausydx30.syd.sap.corp>
To: WS-Choreography List <public-ws-chor@w3.org>
I agree that such multi-party, multi-cast bring complex
dependencies in interactions. In fact the chor. group
had a user case which Peter is describing, but which got
absorbed into TWIST.
One angle on Peter's example is: a request is sent
to a competing set of suppliers, where only one supplier
- the first that consumes it - gets the request. I'm
not sure if this is directly supported through CDL. It
seems that responses would have to sent back from suppliers
prior to the Buyer nominating which one should go ahead.
A more complicated example is the "routing-slip" pattern
as documented in Hoppe. A message is sent once from the
sending side, with an ordering condition in the message
header (say). That condition is used at runtime to determine
the order in which suppliers get the message. It's a bit like
saying I want to send out this message to whole bunch of
parties, but such-and-such should see it before such-and-such -
and the such-and-such-s could well be dynamically, not
statically, determined. 
(By the way, at SAP Research we're currently working on
a set of choreography patterns which are multi-cast focussed.
As part of this we are attempting to map out CDL and BPEL
solutions where possible.) 
Cheers, Alistair.
Dr Alistair Barros 
Senior Researcher - Business Process Mgmt & Enterprise Services 

SAP Research Centre Brisbane
Level 12, 133 Mary Street
Brisbane QLD 4000 Australia 

T  (+61 7) 3259 9554
F  (+61 7) 3259 9599
M  +61 (0) 400 079 447 
W http://www.sap.com/research/ <http://www.sap.com/research/> 
E   <mailto:kim.elms@sap.com> alistair.barros@sap.com 


From: public-ws-chor-request@w3.org [mailto:public-ws-chor-request@w3.org] On Behalf Of Furniss, Peter
Sent: Monday, 18 October 2004 12:39 PM
To: WS-Choreography List
Subject: multiple partners in CDL

I'm not sure if this is lurking somewhere in the issues list, which is why I've not raised it directly.
How should CDL handle a case where there are an indeterminate number of similar partners. For example, the TWIST example shows two potential sellers, but I believe that's just a simplification for explanatory purposes - in reality, the request could be farmed out to any number of sellers, with one being finally selected.  Coping with this would seem to require some sort of collection/set/array construct in CDL - which could be used for relationships, variables, etc.
Is this a current issue ?
(this arose out of working on the actions we got from the coordination/transaction question, but I think is completely orthogonal to that - a completely uncoordinated choreography seeking to find (but not book) the cheapest whatever would have the same requirement)
Peter Furniss
Chief Scientist, Choreology Ltd
web: http://www.choreology.com <http://www.choreology.com/> 
email: peter.furniss@choreology.com <mailto:peter.furniss@choreology.com> 
phone: +44 870 739 0066
mobile: +44 7951 536168

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