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RE: Dubray paper comments + questions

From: Jean-Jacques Dubray <jjd@eigner.com>
Date: Wed, 26 Feb 2003 09:57:38 -0500
To: "'bhaugen'" <linkage@interaccess.com>, <public-ws-chor@w3.org>
Message-ID: <005d01c2dda7$7a8d9050$0502a8c0@JJD>

I think that what Assaf is expressing is that BPSS and the paper I
published on ebPML.org describe message exchange with no specific point
of view (from a party perspective), therefore appearing to be at the
"center". Because these approaches are point of view neutral, they do
not suffer from the same "centricity" syndrome that characterize
BPEL4WS, BPML or even WSCI. In BPEL4WS one describe a collaboration by
specifying the message exchanges from his/her point of view. Of course
the other business partners have to have a mirror definition such that
it works. As I said earlier, WSCI offers a little more flexibility via
the "global model" concept borrowed from WSFL, but in essence WSCI does
exactly like BPEL4WS, it forces each party to describe the collaboration
from his/her point of view.

So instead of introducing this notion of "centralized sequence of
exchange" I think it is fair to say that BPSS offers a "neutral" view of
the choreography while BPEL/BPML and WSCI offers and "interface-bound"
or "party-specific" view of the collaboration.

In all cases, the goal is more or less to achieve state alignment
between collaborating parties.


>>-----Original Message-----
>>From: public-ws-chor-request@w3.org
>>On Behalf Of bhaugen
>>Sent: Wednesday, February 26, 2003 8:21 AM
>>To: public-ws-chor@w3.org
>>Subject: RE: Dubray paper comments + questions
>>Assaf Arkin wrote:
>>> BPEL4WS, BPML, WSCI, etc are based on processes defined for each
>>> communicating agent, dating back to the model proposed in CSP and
>>> refined in pi-calculus and other works in that space. BPSS and EBPML
>>> to express processes as a centralized sequence of exchanges and then
>>> agent has to derive its process by extracting all activities related
>>to some
>>> role.
>>> I think there's conversion from one to the other, but I don't have
>>> that you can move from the CSP model to the centralized one and back
>>> losing some information.
>>I don't think it is accurate to describe BPSS as "centralized".
>>It was derived from the UNCEFACT Business Collaboration
>>Protocol metamodel, which is a state-alignment protocol.
>>That is, the protocol is intended to align the states of
>>"common knowledge" or mutually-agreed-upon
>>state machines, which may be implemented using
>>the Half-Object-Plus-Protocol pattern. (Nothing
>>The protocol does make a distinction between
>>external collaborations (whose states must be aligned)
>>and internal activities (whose states are none of
>>anybody else's business).
>>So if you took a model which included both external
>>and internal activities (in this sense), and moved
>>to BPSS, the BPSS representation would only
>>include the external activities.
>>That does not mean the internal activies would
>>be lost.  It's just a separation of concerns.
>>-Bob Haugen
Received on Wednesday, 26 February 2003 09:57:21 UTC

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