W3C home > Mailing lists > Public > public-ws-chor@w3.org > March 2003

RE: requirements summary

From: Jean-Jacques Dubray <jjd@eigner.com>
Date: Tue, 25 Mar 2003 12:26:14 -0500
To: "'Burdett, David'" <david.burdett@commerceone.com>, "'Jean-Jacques Dubray'" <jjd@eigner.com>, "'Ricky Ho'" <riho@cisco.com>, <jdart@tibco.com>, <Daniel_Austin@grainger.com>
Cc: <public-ws-chor@w3.org>
Message-ID: <012a01c2f2f3$b60104d0$2078050a@JJD>


At the run-time engine level, things gets far more complicated because 
unless there is a party that touches all the "bilateral choreographies",

it is impossible without special run-time to "monitor" the multi-party 
choreography. So the question arise, is the goal of a multi-party 
choreography specification to allow configuration of run-time engines? 
<DB>It depends what you mean by "Monitor". Each party can monitor their
own behavior and the behaviors of the other roles with which they
interact. If one of the parties discovers that some other party is not
behaving properly, then they can raise errors with that party.</DB>

[JJ] Let's take a more concrete example, such as the propagation of
exceptions, if a failure happens (e.g. an operation returned a fault),
to between party B and C. How do we notify party A? Are we expecting
choreography designers to explicitly define the corresponding message
exchange between B and A should this happen? Or are we expecting a more
generic mechanism by which A can be notified of the corresponding
"state" of the choreography. This could be implemented by the run-time
infrastructure. Of course that complicates quite a bit this

In think in the light of this, we should not conclude that binary is a 
special case of multi-party. They may well have both distinct features 
(control flow?) and applications. 
<DB>I'm not sure there is difference, but let's keep exploring ;) </DB> 

[JJ] This is more a question ;-) than an assertion.

I am also wondering if the group wants to keep as a requirement that 
says that in the choreography specification there is no distinction 
between the choreography involving "internal" services as opposed to 
external services. A separate layer of the specification should allow 
for annotating that this particular message exchange is external and may

have more qualifiers. However, at the pure choreography specification 
level, the choreographies should not be distinguished. 
<DB>Am I right in assuming that by "internal" you mean within a "domain
of control", e.g. a business, and that "External" means between domains
of control, e.g. between businesses. If so then although, in theory,
they can be expressed in the same way, there are significant *practical*

1. External choreographies, between domains of control, will be used by
MULTIPLE (perhaps millions) of different parties and therefore the
definition MUST be abstract to avoid multiple definitions of essentially
the same choreography.

2. For Internal choreographies, within a domain of control, there is
only ONE implementation and therefore the definition can be very
concrete and does not need to be abstract at all.

[JJ] I agree that this is generally true but large companies might also
want to benefit from this abstraction. We have customers that have 30
ERP implementations, I also often talk about this large A&D company that
has 84 procurement systems. 


>>-----Original Message----- 
>>From: public-ws-chor-request@w3.org 
>>On Behalf Of Ricky Ho 
>>Sent: Monday, March 24, 2003 7:06 PM 
>>To: jdart@tibco.com; Daniel_Austin@grainger.com 
>>Cc: public-ws-chor@w3.org 
>>Subject: Re: requirements summary 
>>I was originally thinking that a multi-party choreography can always 
>>broken down into multiple "inter-dependent" bi-party choreography. 
But I 
>>am convinced that this is NOT always possible. 
>>So I think bi-party choreography is a special case of multi-party 
>>choreography.  Bi-party choreography has some interesting properties 
>>can simplify the modeling.  (e.g. Bi-Party choreography doesn't need 
>>worry about dynamic participation because any change of a binding can 
>>simply terminate the choreography). 
>>I think we should covered multi-party choreography.  In additional, we

>>also need to investigate this special subset called bi-party 
>>Best regards, 
>>At 02:28 PM 3/24/2003 -0800, Jon Dart wrote: 
>>>Daniel_Austin@grainger.com wrote: 
>>>>2. Multi-party vs. bilateral choreography: there is some skepticism 
>>>>that modelling bilateral interactions is sufficient. 
>>>>       I certainly don't think that is it sufficient to model only 
>>>>transactions. Many business transactions have multiple actors, and 
>>>>to build standards that will work for common service transaction 
>>>Note that it is not exactly all or nothing here. BPSS for example 
>>>"MultiParty Collaborations", but does so by composing them out of 
Received on Tuesday, 25 March 2003 12:33:06 UTC

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