W3C home > Mailing lists > Public > public-ws-chor@w3.org > December 2005

Re: WS-CDL or abstract BPEL

From: Charlton Barreto <charlton_b@mac.com>
Date: Thu, 01 Dec 2005 13:35:37 -0800
Message-ID: <12121690.1133472937096.JavaMail.charlton_b@mac.com>
To: Tonny Holdorf <tonny.holdorf@gmail.com>
Cc: public-ws-chor@w3.org

The fundamental differences between orchestration and choreography are another differentiator. With its single participant, local view, orchestration languages are unable to provide a non-opaque view of the full set of participants in interactions. With BPEL, whether Abstract or Executable, this is true even for distributed participants within the trusted domain of the business process. This prevents active monitoring and management of a distributed process, which is required for critical operations, whether public or private. It also requires rather elaborate mechanisms for maintaining consistency between activities in a distributed process, which impacts how well BPEL engines can perform. 

Choregraphy, in providing a global view and an interaction model for one or more participants, focusses on the protocol; participants, distributed within or across an organisation's trusted domain, cooperate by message exchange, leaving the abstract or executable definition of a party's internal logic. Choreography and orchestration complement one another to provide a complete view by combining the global and local views, enabling active monitoring and management of distributed interactions or processes. With CDL, choreography descriptions can be generated to BPEL, which enables coordination of distributed interactions or processes in a transparent manner, while allowing each layer to be optimised according to their function. 

On Thursday, December 01, 2005, at 04:53AM, Tonny Holdorf <tonny.holdorf@gmail.com> wrote:

>Hello everybody,
>I am totally new to this community, so please bear with me if I have  
>gotten something wrong.
>I am trying to get a view of the pros and cons of WS-CDL versus  
>abstract BPEL for modeling business collaborations and protocols. In  
>a thread on the Theserverside:
>Steve Ross-Talbot linked to the paper by Marco Carbone Kohei Honda  
>and Nobuko Yoshida. Reading the paper made me wonder if the WS-CDL  
>and the abstract BPEL work groups and specifications are pursuing the  
>same goal. Steve suggested that I post my questions here. So here  
>they are:
>In the paper linked to above (i.e. the paper by Marco Carbone Kohei  
>Honda and Nobuko Yoshida) two formal calculi are described: a  
>'global' calculus that models business processes from a global  
>perspective and the pi-calculus that models the same processes as a  
>set of local endpoint behaviors. The global calculus is similar to WS- 
>CDL and the main point of the paper is that processes modeled with  
>the global calculus (WS-CDL) can be translated to the pi-calculus.
>Reading the paper made me wonder: Why is a global description of the  
>service collaboration as in WS-CDL better than a set of local  
>descriptions that each describes the behavior of the participating  
>services (e.g. as a set of abstract BPEL descriptions)? Would a set  
>of abstract BPEL descriptions for each of the collaborating services  
>and a global WS-CDL description for the collaboration as a whole not  
>just be different representations of the same thing? If not, what  
>expressive power is added by the global WS-CDL description compared  
>to a set of abstract BPEL descriptions for each end point.
>Also, many complicated network protocols, e.g. TCP, have been  
>specified just fine by descriptions of endpoint behavior such as  
>state machines. Why is a global specification needed?
>Best Regards
Received on Thursday, 1 December 2005 21:35:54 UTC

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