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Re: WS-CDL and (polyadic) Pi-Calculus

From: Marco Carbone <carbonem@dcs.qmul.ac.uk>
Date: Tue, 17 Jan 2006 13:43:53 +0000
Message-Id: <4B20A94E-9F5C-4C55-8EDA-97E0B89F16BC@dcs.qmul.ac.uk>
Cc: "Steve Ross-Talbot" <steve@pi4tech.com>, <public-ws-chor@w3.org>
To: "Paul Bouche \(HPI\)" <paul.bouche@hpi.uni-potsdam.de>

Dear Paul,

> In answering that question I am trying to analyze the concrete  
> relationship of WS-CDL and Pi, ie what concepts in WS-CDL come from  
> Pi.

there is a concrete relationship between WS-CDL and the pi-calculus  
indeed. WS-CDL was designed based on some features of the pi  
calculus, e.g. parallel composition, choice and, of course, channel  
passing. This does NOT imply that they are the same or that WS-CDL is  
an extension of the pi calculus. As you noticed, WS-CDL is  
communication-centered, instead the pi-calculus is based on  
communication among peers (pi processes). An accurate analysis of the  
relationship is to come soon in Q22006 as mentioned by Steve (that  
would be part II of [3]). Meanwhile you can take a look at [3] where  
the connection between pi and CDL is discussed through examples.


> Thx,
> Paul
> Steve Ross-Talbot wrote:
>> Hi Paul,
>> I am referring to [3] when talking about formal treatments. [1]  
>> was an  early thought about how to do it and has given rise to  
>> [3]. Whereas [2]  is Nick's partial treatment which is now  
>> subsumed by [3] and what will  follow in Q22006 (Quarter 2 2006).
>> You are correct that workunits are not influenced by pi-calculus.  
>> They  are more data-flow influenced. But they are representable in  
>> pi and  have a formal treatment in GC and through to the EPC. And  
>> yes pi is not  typed as such, although there is the notion of  
>> sorts which is much the  same.
>> What is it that you are trying to do with respect to WS-CDL?
>> Cheers
>> Steve T
>> On 17 Jan 2006, at 11:32, Paul Bouche ((HPI)) wrote:
>>> Hi,
>>> thanks Ingo and Steve for your answers.
>>> The IMHO goes for all I am about to say.
>>> Ingo, channels and sending of channels, I clearly see as inspired  
>>> from  Pi, but the work unit concept, all the concepts finalizer,  
>>> exception,  roleType, participantType, bahaviour and state  
>>> mangement concepts I  don't see how the were inspired from Pi.  
>>> Those are added and more  high-level than Pi. The grouping  
>>> concepts for activities are clearly  those of Pi: Seqeunce,  
>>> Parallel, Choice. Yet there is a  while-loop-grouping construct  
>>> which is also not found in Pi. Surely  all these concepts can be  
>>> expressed with Pi-Calculus with more or less  effort. The  
>>> exchange interaction concepts also is clearly inspired by  Pi. Pi  
>>> does not differentiate between variables, channelTypes,   
>>> channelType instances, names of channels, tokens etc. This is  
>>> another  high-level addition. Also from my knowledge Pi-Calculus  
>>> is not typed  at all, it does not even have a data flow centric  
>>> concept but it is  all process centric or oriented.  This  
>>> orientation I cannot clearly  see in WS-CDL. Yet this may also  
>>> not be possible because of the goals  for WS-CDL, and also  
>>> because of that high-level constructs had to be  added.
>>> Steve are you refering to [1], [2] and [3] when you talk about  
>>> "Global  Calculus"? What does "Q22006" mean - 12/22/2006 - which  
>>> would be  December 12th 2006?
>>> Thank you for you inputs!
>>> Paul
>>> [1] Carbone, Honda, Yoshida, "Programming interaction with  
>>> Types" ,   http://www.w3.org/2002/ws/chor/5/06/F2FJune14.pdf
>>> [2] Kavantzas, "Aggregating Web Service: Choreography and WS- 
>>> CDL",  http://lists.w3.org/Archives/Public/www-archive/2004Aug/ 
>>> att-0017/WS- CDL-April2004.ppt
>>> [3] Honda, Yoshida, et. al. "A Theoretical Basis of   
>>> Communication-Centred Concurrent Programming",  http:// 
>>> lists.w3.org/Archives/Public/public-ws-chor/2005Nov/att-0015/  
>>> part1_Nov25.pdf
>>> Steve Ross-Talbot wrote:
>>>> Deal Paul,
>>>> Yes the channels where inspired by pi-calculus. They are a  
>>>> channel or  port pairing. The work of our invited experts looks  
>>>> at providing a  new calculus called CG (Global Calculus). When  
>>>> we project  participants we do so to an EPC (End Point Calculus)  
>>>> which is  pi-calculus with session types. The session  
>>>> information comes from  the identity tokens described as part of  
>>>> a channel type. This EPC is  what we use to enforce liveness and  
>>>> other relevant properties  (bi-simulation etc).
>>>> The plan is to publish the finished treatment of GC and EPC  
>>>> sometime  in Q22006 as a working note.
>>>> Hope this helps
>>>> Steve T

Marco Carbone

Dept. of Computer Science
Queen Mary University of London
Mile End Road
E1 4NS London
United Kingdom

Phone: +44 (0) 207 882 3659
Fax:      +44 (0) 208 980 6533
email:   carbonem@dcs.qmul.ac.uk
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Received on Tuesday, 17 January 2006 17:56:37 UTC

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