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Subject: Re: [wsbpel] Link semantics and control dependencies
the only other one I can think of is when the link order contradicts the order of execution, e.g. if the first activity in a sequence is the target, and the second activity is the source. assaf Satish Thatte wrote: >Is there a case other than a link targeting an activity sourced at a >parent activity in the nesting structure? IOW is this an example or the >only case? > >-----Original Message----- >From: Assaf Arkin [mailto:arkin@intalio.com] >Sent: Monday, April 04, 2005 7:40 PM >To: Satish Thatte >Cc: Dumas, Marlon; wsbpel@lists.oasis-open.org >Subject: Re: [wsbpel] Link semantics and control dependencies > >Since A3 is allowed to begin (when selected) before A1 completes (in >fact, A1 must complete after A3), a link dependency cannot be etablished > >between A1 and A3, so the link is invalid. Perhaps, we should be more >clear about this in the spec, though I believe it says something about >links not being valid when they contradict ordering of activities (e.g. >links that reverse order of sequence): > >It is illegal to declare a link if a control dependency cannot be >established between the source activity and target activity, for >example, if the target activity is nested within the source activity >(and vice versa), and therefore must complete before the source activity > >has completed. > >Assaf > >Satish Thatte wrote: > > > >>Marlon, >> >>I am trying to fathom the link from A1 to A3. Do you mean that A1 is >>the switch activity and A3 is a nested case within the switch and there >>is a link from A1 to A3? If so then this is pathological. I realize >>that we probably don't ban it today explicitly but there is no way to >>have A3 execute in this case, regardless of the A4 conundrum. >> >>Satish >> >>-----Original Message----- >>From: Dumas, Marlon [mailto:marlon.dumas@sap.com] >>Sent: Thursday, March 31, 2005 1:30 AM >>To: wsbpel@lists.oasis-open.org >>Subject: [wsbpel] Link semantics and control dependencies >> >>Hi, >> >>I believe that the following two fragments of the spec. contradict each >>other and I would like to gather second opinions about it: >> >>In Section 12.5.1 (Link Semantics) >>"If, during the performance of structured activity S, the semantics of >>S dictate that activity X nested within S will not be performed as >>part of the behavior of S, then the status of all outgoing links from >>X is set to negative. An example is an activity within a branch that >>is not taken in a switch activity..." >> >>In Section 13.4.2 (Default Compensation Order): >>"If an activity A must complete before activity B begins, as a result >>of the existence of a control path from A to B in the process >>definition, then we say that B has a control dependency on A. Note >>that control dependencies may occur due to control links in a <flow> >>as well as due to constructs like <sequence>." >> >>To illustrate this contradiction, consider the following example: >> >><flow name="F"> >>link x1 goes from A1 to A3 >>link x2 goes from A3 to A4 >> >>A1 >><switch name="Sw"> >> case C1: A2 >> case C2: A3 >></switch> >>A4 [joinCondition = "not x2"] >> >></flow> >> >>Let's now consider the following execution: Flow F starts, and thus >>action A1 and switch "Sw" are executed. Note that at this point A4 is >>ready to start but does not start because its incoming link x2 has not >>yet been determined. Let's now assume that condition C1 evaluates to >>true and thus the corresponding branch is taken which results in >>activity A2 being executed. According to the first quote from the >>spec. above, the status of link x2 is then set to negative since >>branch A3 was not taken. The joinCondition at A4 ("not x2") then >>evaluates to True, and this results in A4 being executed. Note that at >>this point in time, A1 has not yet completed. >> >>This seems to contradict the second quote above. Indeed, there is a >>control path from A1 to A4 (i.e. a control link from A1 to A3 and >>another one from A3 to A4), which means that A4 has a control >>dependency on A1. Hence A4 cannot start before A1 has completed. >> >>Does anybody find any flaws in my reasoning? >> >>Thanks >> >>marlon >> >>--------------------------------------------------------------------- >>To unsubscribe from this mail list, you must leave the OASIS TC that >>generates this mail. You may a link to this group and all your TCs in >>OASIS >>at: >>https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >> >> >>--------------------------------------------------------------------- >>To unsubscribe from this mail list, you must leave the OASIS TC that >>generates this mail. You may a link to this group and all your TCs in >> >> >OASIS > > >>at: >>https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php >> >> >> >> >> >> > > > >
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