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RE: requirements summary

From: Patil, Sanjaykumar <sanjay.patil@iona.com>
Date: Tue, 25 Mar 2003 10:14:47 -0800
To: "Jean-Jacques Dubray" <jjd@eigner.com>, "Ricky Ho" <riho@cisco.com>, <jdart@tibco.com>, <Daniel_Austin@grainger.com>
Cc: <public-ws-chor@w3.org>

A multi-party choreography definition will most likely also include information above and beyond the set of binary collaborations. For example, a multi-party definition will also include the temporal and logical conditions which decide the valid order of the binary collaborations. I guess, Ricky's patient-doctor-receptionist scenario clearly points out such a need.

However, I am not sure whether a multi-party choreography definition is also pivotal to enabling central monitoring of the overall choreography. Let us consider the following two scenarios (based on whether the participants belong to the same or different domains of control):

a> When the participants belong to different domains of control: Each participant in this case would execute its share of the binary collaborations as well as its share of ensuring the overall order of the binary collaborations. Note that, in this scenario, there is perhaps no need as such to monitor the overall choreography, besides each side monitoring its own compliance in meeting its obligations.

b> When the participants belong to the same domain of control: In this case, a need for central monitoring may sound a bit more obvious. Now there is a choice of the governance of the participants, that is, each participant can either be autonomous (just like the above scenario of different domains of control) or is governed by a central authority (runtime engine). Based on the choice (perhaps an implementation decision), the infrastructure for monitoring would differ. However, I don't see how a particular specification of the choreography definition will improve or reduce the ability to monitor the overall choreography.

Sanjay Patil
Distinguished Engineer
IONA Technologies
2350 Mission College Blvd. Suite 650
Santa Clara, CA 95054
Tel: (408) 350 9619
Fax: (408) 350 9501
Making Software Work Together TM

-----Original Message-----
From: Jean-Jacques Dubray [mailto:jjd@eigner.com]
Sent: Tuesday, March 25, 2003 7:30 AM
To: 'Ricky Ho'; jdart@tibco.com; Daniel_Austin@grainger.com
Cc: public-ws-chor@w3.org
Subject: RE: requirements summary


It is also interesting to introduce the perspective of why a multi-party
can be used for?

Both a multi-party and binary can be used to represent what is going to
happen (see Assaf's presentation on causality). 

A binary collaboration can easily be used as part of an agreement, as
well as to configure run-time engine that "monitor" the choreography
(firewall concept).

In the case of a multi-party, we might want to ask whether the goal is
simply to represent what is going to happen such that each party can
infer what they need to do. Hence decompose the multi-party into
bilateral behavior (which will itself be decomposed in unilateral

Is there a need to establish multi-party agreements based on a
multi-party choreography definition? 

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?

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.

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.



>>-----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 13:16:22 UTC

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