999 2005-01-10 15:58:18 +0000 Short Circuit Evaluation 2005-08-03 13:40:27 +0000 1 1 1 Unclassified WS Choreography Last Call Comment: Confirmed Closed unspecified PC Windows 2000 CLOSED FIXED http://lists.w3.org/Archives/Public/public-ws-chor-comments/2005Jan/0002.html P2 normal -- 1099 1 martin.chapman martin.chapman martin.chapman oldest_to_newest 2809 0 martin.chapman 2005-01-10 15:58:18 +0000 The CDL specification ( Web Services ChoreographyDescription Language Version 1.0 W3C Last Call Draft 17 December 2004 <http://www.w3.org/TR/2004/WD-ws-cdl-10-20041217/> http://www.w3.org/TR/2004/WD-ws-cdl-10-20041217/ ) should specifically state whether the short circuit evaluation of Boolean conditions is mandated or prohibited. Short circuit evaluation of Boolean conditions does not alter the value of the condition but in CDL it can alter the time at which that condition evaluation becomes available, which in turn can alter the evolution of a choreography. My concern is that if different endpoint projections make the opposite assumption then erroneous behaviour could result. Consider a Boolean condition of the form Variable>100 AND hasDurationPassed(2hours) not exactly the correct syntax I am sure but hopefully you see the point. With this condition as the value of a guard and block =true and assuming the variable value is available immediately and is such that Variable>100 is FALSE then if short circuit evaluation is mandated then the condition evaluates to FALSE immediately and the choreography moves on. However, if short circuit evaluation is prohibited then the condition evaluates to FALSE only after two hours has elapsed - very different behaviour in time, and as other interactions may also be time dependent we have to remember that CDL can yield descriptions with some dependency on time. Therefore: (!!) 1) Rationale: Short circuit evaluation of Boolean conditions should be explicitly mandated or prohibited so that different tools, endpoint projections, etc do not make contrary choices of how to evaluate. Add to section 2.4.3 Expressions (or elsewhere if a better place can be found): Boolean conditional expressions MUST use short circuit evaluation techniques whatever the setting of the block attribute. That is once the value of a conditional expression can be evaluated and the result will no longer change if further variables become available or time based functions become true, the conditional expression returns its value. Note: If it is thought this incorrect and we should not permit short circuit evaluation for some good reason then we should specifically prohibit it and add text similar to that above but stating MUST NOT instead. Best Regards Tony 4159 1 martin.chapman 2005-02-14 20:34:26 +0000 From meeting on 11-jan-05 http://lists.w3.org/Archives/Member/member-ws-chor/2005Jan/att-0002/2005-01- 11_WS-Chor_Notes.txt: Discussion deferred as deemed to be a technical issue. 4018 2 martin.chapman 2005-03-08 10:40:36 +0000 Discussed at feb-mar 05 f2f: http://lists.w3.org/Archives/Member/member-ws-chor/2005Mar/att- 0001/Ws_Chor_f2f__Feb-Mar_2005_-0.txt Use Xpath rules of left to right evaluation. 4028 3 martin.chapman 2005-03-08 11:05:18 +0000 add note to spec to say reply on xpath left to right evaluation. 3426 4 martin.chapman 2005-05-10 14:40:04 +0000 Tony has been informed of the group's decision [1] and we are awaiting confirmation. Category changed to LCC: Closed. [1] http://lists.w3.org/Archives/Public/public-ws-chor- comments/2005May/0007.html 3173 5 martin.chapman 2005-05-17 22:06:31 +0000 Tony agrees the resolution is acceptable: http://lists.w3.org/Archives/Public/public-ws-chor-comments/2005May/0030.html 3057 6 gritzinger 2005-05-25 19:07:12 +0000 Section 2.4.5 Choreographies, bullet on the ‘complete’ attribute: This Boolean conditional expression MUST use short circuit evaluation according to the XPath left to right rules.Added same sentence twice to Section 2.4.6 Workunits, bullets on ‘guard’ and ‘repeat’ attributes. 5348 7 martin.chapman 2005-08-03 13:40:27 +0000 correcting status to closed.