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Re: New Paper available for PDF download: Workflow is just a Pi process (or WFM is not BPM)

From: Andrew Berry <andyb@whyanbeel.net>
Date: Mon, 17 Nov 2003 20:57:15 +1000
Cc: public-ws-chor@w3.org, W.M.P.v.d.Aalst@tm.tue.nl
To: Howard N Smith <howard.smith@ontology.org>
Message-Id: <CE1A381A-18EC-11D8-B79E-0003936786BC@whyanbeel.net>


You have a fundamental problem with the choice of Pi Calculus: there is 
no concept of locality or partial state. In choreography and web 
services in general, you can guarantee that participants (processes) 
are physically distributed and need to make choices based on a partial 
view of state.  To successfully model, program and reason about these 
processes, you need to be able to identify and reason about partial 

Consider your deferred choice semantics.  If the processes identified 
as choices are physically distributed, you *cannot* make a choice 
without synchronisation of processes because distinct choices can be 
made in a truly concurrent fashion.  Pi Calculus has no way of 
identifying this issue, let alone reasoning about it.  Explicit 
synchronisation processes, while solving the problem for a given 
process, require that the programmer reason about distribution and 
locality outside the bounds of the Pi Calculus semantics.  I would 
therefore argue that a worflow and in particular a choreography is not 
a Pi Process.



On Wednesday, November 12, 2003, at 03:00  AM, Howard N Smith wrote:

> Choreography pioneers,
> Following a short conversation with Steve R-T, he agreed for me to 
> send you this paper.
> It is intended as a draft for discussion.
> The paper is new information. It shows how, based on BPML, it is 
> possible to model all
> of the advanced workflow patterns identified by workflow theorists, 
> whereas most workflow
> engines only support approx 50% of patterns directly and very few of 
> the advanced patterns.
> In addition, it gives insights into the BPML implementation inherent 
> to a BPMS, and how a
> BPMS is able to support many process models not supported by workflow 
> technology.
> Screenshots from Intalio|n3 BPMS are given as examples. Further, the 
> workflow engine itself can
> be modelled in BPML, as reusable processes for use in end-to-end 
> processes. The paper was
> written to more fully explain the work of BPMI.org and its direction 
> in creating BPMS foundation
> technologies.
> Peter Fingar and I have taken great care with this paper, and do hope 
> it adds to the
> understanding of BPML/BPMI/BPMS direction. While the paper cannot 
> present proof of
> these claims, you can consider it a report on the work so far.
> The paper can be downloaded from:
> http://www.bpm3.com/picalculus/workflow-is-just-a-pi-process.pdf
> Regards,
> Howard
> ---
> New Book - Business Process Management: The Third Wave
> www.bpm3.com
> Howard Smith/CSC/BPMI.org
> cell             +44 7711 594 494 (worldwide)
> home office +44 20 8660 1963
Received on Monday, 17 November 2003 05:58:36 UTC

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