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Subject: RE: Collaboration Services (was: Business Service Interface)
<Stefano Pogliani> I did not fully understand the position which is expressed in your message. What Bob was saying (if I interpret correctly) is, in summary, that : - sequencing is not a pattern that could be generally used to model the business intelligence - that some software (Bob mentions two levels) is required to manage long collaborations (and their status) </Stefano Pogliani> <BobHaugen> Stefano, thank you for a careful reading. Slight clarification: I would not deny the usefulness of simple sequencing in some cases, but there are other important cases where it is inadequate and pre and post conditions would also be simple and work well. I believe there is general agreement in the BP group now that pre and post conditions are important choreography hooks. </BobHaugen> I think that defining preconditions and postconditions on "segments" of business processes (where a segment is something like an edge in a graph of business states) would without doubt be general enough for anything to be choreographed for a number of years. My problem is that it is _so_ general that it is difficult to see how the resulting processes will "modularize out" for implementation levels. Here is a case that I hope illustrates my point. A large motherboard manufacturer needs weekly small parts (capacitor resistors etc) from its multiple suppliers, say 10 large suppliers. It wants aggregate numbers of capacitor C for the upcoming production run, and knows no one supplier will be able to meet that aggregate number. So the manufacturer broadcasts to each supplier to say how many C (at what cost) can be made available by time T, and to reserve those quantities for 5 hours, or until they get a release-or-order document. Meanwhile the precondition for responding to the availability messages might be phrased as "wait until a majority of suppliers have responded or 5 hours elapse" or it might be "wait until the aggregate available C crosses the threshold or 5 hours elapse" or "(wait until the optmized price per C is below X and aggregate available C crosses threshold) or 5 hours elapse". The point here is that while middleware products might coordinate processes where the join precondition is in terms of number of messages received, if the precondition wanders into optimizations over business quantities, normally we would think that an application needs to be specially constructed/confgiured to do those jobs. So it is hard to see where to draw the line at session layer coordination of processes and more substantial business quantity coordination of BPs.
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