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RE: Dubray paper comments + questions

From: bhaugen <linkage@interaccess.com>
Date: Wed, 26 Feb 2003 07:21:04 -0600
To: public-ws-chor@w3.org
Message-id: <001501c2dd99$ea940860$b8eafea9@PC1>

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 08:22:03 UTC

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