As and when the formal semantics of WS-CDL are published (there are some early version on the w3c lists - look for Kohei Honda - you will see that WS-CDL has a global calculus that precisely defined what it can express along with some properties as to what constitutes a good choreography and therefore a bad choreography. The same working note will also cover what is called end point projectiion (EPP). EPP results in a service centric view of what a service/process must do to meet the obligation placed on it by the choreography. In this regard EPP, which is not a standard but a formalism to be used by vendors, is akin to abstract BPEL but not the same. I would very much like to know if Abstract BPEL will be a true standard (part of WS-BPEL) and if it meets the needs of EPP. If it does then we have a very good way of using WS-CDL and BPEL in nice clean composable way. Frank any ideas?
Cheers Steve T On 23 Jul 2006, at 07:12, ash galal wrote: > Hi Alexis > I think choreography is what and how too. > It covers two aspects: web service chorography interface and semantic > web service chorography. > Web service chorography interface as described in W3C, is a > specification and an XML-based language for describing interfaces used > to specify the flow of messages at interacting web services. > Semantic web service chorography, deals with the description of the > external message interface and conversational pattern exposed by a > service that allow others to consume its functionality. > I think web service chorography definition covers semantic web service > chorography definition too. I am confused a little bit in such > definitions. > Semantic web service chorography could be considered as what while web > service chorography interface is both what and how. > Composition is a result of combining simple objects data types into > more complex data types or function calls into calling functions. I > think it is low level than Orchestration. > Orchestration describes the automated arrangement and management of > complex middleware or services. > Usually orchestration is an engine (how) often used for BPM, allowing > developers to quickly orchestrate complex business processes involving > multiple disparate systems. > > Ash Galal > > Alexis Richardson <[EMAIL PROTECTED]> wrote: >> I don't know if this helps people to make a quick distinction, as it >> is certainly a simplification :-) Nevertheless, one could say: >> >> - the choreography is the 'what' >> - the orchestration is the 'how' >> >> It is very important to not confuse the what from the how. >> >> I don't know what composition is, other than that two whats always >> make another what, and two hows may make another how if sensibly >> combined. >> >> Cheers >> >> alexis >> >> On 7/20/06, Gervas Douglas <[EMAIL PROTECTED]> wrote: >> > I think it would be really useful if we could reach some sort of a >> > consensus on these definitions. "Orchestration" and "choreography" >> in >> > particular are typical of terms which spring up into public >> discourse >> > and then get bandied about as faddish terms, especially by >> markitechts >> > and CBSOs, with most people not having a precise idea of their >> meaning. >> > >> > Gervas >> > >> > --- In [email protected], Teresa Jones >> > <[EMAIL PROTECTED]> wrote: >> > > >> > > As a musician, I would say that all words are incorrectly used in >> IT.... >> > > However, I would perhaps try to define: >> > > Composition - putting together 'services' to make a 'composite >> > application' >> > > - i.e. one that may then be fairly fixed for some time. >> > > Choreography - the ability to sequence (loosely) services (which >> > could be >> > > human or computer) to be a business process. >> > > Orchestration - probably the same as the above, but perhaps at a >> higher >> > > level? >> > > >> > > Teresa >> > > >> > > _____ >> > > >> > > From: Ashley at Metamaxim [mailto:[EMAIL PROTECTED] >> > > Sent: 19 July 2006 15:10 >> > > To: [email protected] >> > > Subject: Re: [service-orientated-architecture] Orchestration, >> > Choreography, >> > > and Composition >> > > >> > > >> > > >> > > >> > > Todd wrote: >> > > >> > > > I thought I'd turn this into a group exercise and see how all >> of you >> > > > define it. (i.e., Orchestration, Choreography, and Composition) >> > > >> > > Excellent. This should be fun! >> > > >> > > In my view, Choreography defines a behavioural protocol to which >> > multiple >> > > parties must (or should) adhere when engaged in a service based >> > > collaboration. I am sure that Steve R-T will give us the >> definitive >> > > definition of Choreography! >> > > >> > > Like you, Todd, I am not clear whether there is any real >> difference >> > between >> > > Orchestration and Composition. Perhaps Orchestration is the means >> by >> > which >> > > Composition is achieved? >> > > >> > > Rgds >> > > Ashley >> > > >> > > >> > > >> > > >> ********************************************************************* >> > > IMPORTANT NOTICE >> > > >> > > The contents of this e-mail are privileged and confidential and >> > > intended for the addressee at the specified e-mail address only. >> > > Its contents may not be copied or disclosed to anyone other than >> > > the intended recipient. 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