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Subject: Re: [wsbpel] implicite links of the runtime engine (was: Implicit<sequence> macro)
Satish Thatte wrote: >All true, except for the simple matter of analyzing the implications of >concurrency for access to shared data or being able to recognize the >patterns where concurrency is absent and thus concurrency control is not >required. In particular, if a sequence has incoming and outgoing links, >and is now replaced with a flow with links itself, I submit that >recovering the original pattern and its simple inexpensive >implementation would be challenging. > > Again the assumption is that you have to do it anyway for the flow activity to determine that some activity A can access shared data written by some activity B, where A and B are executed in different paths but are synchronized using a link. Doing it for a sequence of activities is fairly trivial since you join condition tends to involve one mandatory input link ;-) >In other words, we would be raising the bar for implementers of both >tools and runtime engines, especially if we expect them to cater to the >prejudices of those who prefer the "block structured" approach rather >than the "linking activities" approach that Assaf seems to like these >days. > > From an execution perspective I have a strict preferrence for linking activities approach and always did. My preference can be summed up as "the less constructs the better". If the execution engine already has to deal with the complexity of <flow>, then I don't see an evidence to support the need for <sequence>. There's a different set of requirements when you start tackling modeling and addressing visual notations. A language that is intended to address modeling would also include requirements for modeling and visual representation. Such requirement would incidentally suggest the introduction of a <sequence> activity, more looping constructs and other notational aids. Which category are we trying to fit in? arkin >Satish >
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