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

RE: Dubray paper comments + questions

From: Assaf Arkin <arkin@intalio.com>
Date: Wed, 26 Feb 2003 13:19:30 -0800
To: "Jean-Jacques Dubray" <jjd@eigner.com>, "'bhaugen'" <linkage@interaccess.com>, <public-ws-chor@w3.org>
Message-ID: <IGEJLEPAJBPHKACOOKHNOEDEDEAA.arkin@intalio.com>



> -----Original Message-----
> From: public-ws-chor-request@w3.org
> [mailto:public-ws-chor-request@w3.org]On Behalf Of Jean-Jacques Dubray
> Sent: Wednesday, February 26, 2003 6:58 AM
> To: 'bhaugen'; public-ws-chor@w3.org
> Subject: RE: Dubray paper comments + questions
>
>
> 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.

Indeed. We have elected to base these languages on formal models for
defining processes as communicating agents, in which the overall process is
expressed in terms of the roles communicating and recursively divided into
the interaction between participants, forcing each participant to bind to
that interface which is particular to its service.

This is both consistent with the notion of Web services as described by the
WSA in general and WSDL specifically, and formal models, and naturally the
way in which the Web works.

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

Absolutely true!

arkin

>
> JJ-
>
>
>
> >>-----Original Message-----
> >>From: public-ws-chor-request@w3.org
> [mailto: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
> >>later
> >>> refined in pi-calculus and other works in that space. BPSS and EBPML
> >>prefer
> >>> to express processes as a centralized sequence of exchanges and then
> >>each
> >>> 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
> >>evidence
> >>> that you can move from the CSP model to the centralized one and back
> >>without
> >>> 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
> >>centralized.)
> >>
> >>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 16:21:49 UTC

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