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Subject: Re: [wsbpel] implicite links of the runtime engine (was: Implicit<sequence> macro)
Assaf Arkin wrote: > Satish Thatte wrote: > >> Popping up a level, the basic point is that minimality is in the eye >> of the beholder. Why stop with eliminating sequence? Links can be >> emulated by message based synchronization. Concurrency (flow) can be >> emulated by a spawn feature, using message passing to emulate shared >> state. In the end we have message passing including port reference >> passing, spawn, some notion of abstraction (declaration) and some >> form of recursion and not much else, i.e., the pi calculus. Pi is >> provably able to emulate everything including XML data. But I doubt >> it would satisfy most members of the TC as the specification we >> produce. There is some element of judgment involved in deciding what >> is minimal enough for BPEL -- emulation is not a conclusive argument. >> >> >> > Indeed some forms of "simplicity" actually introduces a lot of > complexity ;-) > >> I am sure none of you will disagree at this level, although the only >> argument I have heard for eliminating sequence so far is that it can >> be emulated with flow and links. >> > I'm going to start by disagreeing for a second and see what the > consequences are. > > Just as a reminder, my criteria is to "reduce the complexity of the > specification while allowing interoperability/portability" (without > which you don't really need a standard, do you?). > > If you go all the way to pi-calculus you end up with a situtation > where two systems may decide to use different WSDL operations or > construct different messages for the same process definition since > there is no interpretations of how names/actions should be mapped to > WSDL. So to answer Edwin's question, you lose interoperability , you > might as well have no spec. ^== Sorry, it was David's question, I was looking at the wrong e-mail header ;-) > > Or, you can formalize the manner in which WSDL operations are used > with a pi-calculus like definition, but then you need to add further > rules to the specification. Off the top of my head I can think of > two/three rules and I can ensure you they are more complex than the > definition of sequence. So while turning the language from a > high-level model to a low-level model, you would significantly > increase the complexity of the specification. > > So here's a very simple criteria for accepting/rejecting constructs > that would accept the removal of <sequence> but would clarify exactly > why you would not attempt to take <flow> out of existence. > > Does this help? > > arkin >
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