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Subject: RE: [wsbpel] Re: completionHandler example
?? You mean the parent of the completed scope? Which has no access to the data of the completed scope? -----Original Message----- From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Wednesday, October 06, 2004 11:39 AM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example Right, that is why I said this event is caught by the parent scope. -----Original Message----- From: Satish Thatte [mailto:satisht@microsoft.com] Sent: Wednesday, October 06, 2004 2:31 PM To: Chris Keller Cc: wsbpeltc; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example Don't you think it will be strange to say that the scope is finished, existing events will be terminated, no new events will be accepted, *except* for this special beast which we choose to call an event? It is also obviously different in having a very different "communication channel". -----Original Message----- From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Wednesday, October 06, 2004 11:00 AM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example I don't think we need any special pleading. Since the current specification says even under termination a scope does not complete until all its event handlers have completed (either normally or abnormally via forcedTermination). It seems the complete event is naturally the last event and doesn't need to cut in front or cancel them. In fact one could argue that they must be caught by the parent scope's event handlers. -----Original Message----- From: Satish Thatte [mailto:satisht@microsoft.com] Sent: Wednesday, October 06, 2004 1:32 PM To: Chris Keller Cc: wsbpeltc; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example The reason I call it false economy is that one will have to do a bunch of special pleading -- this event handler will cut in front of the queue of all the other pending events and cancel them. This event handler is not really concurrent with the scope -- it only runs after the activity in the scope has be completed (or forced to terminate). This event is not external and has no communication channel. Etcetera. Reminiscent of the special pleading for the forcedTermination fault handler. -----Original Message----- From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Wednesday, October 06, 2004 6:36 AM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example I think that was already clear from your comments, but thanks for helping think this through anyway. I believe in order to make informed decisions about proposals it is necessary to look at it from different angles. As you would expect I disagree with your false economy statement and rather think of it from the standpoint of "practical extensibility". Given that extensible typed events and a mechanism for handling them have already proven to be useful in so many applications. -----Original Message----- From: Satish Thatte [mailto:satisht@microsoft.com] Sent: Wednesday, October 06, 2004 12:58 AM To: Chris Keller Cc: wsbpeltc; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example To be clear I am not really endorsing this, but it is interesting and instructive to think through -- as a concrete resolution I am afraid this is false economy of the same sort that we are likely to end up having to reverse in the case of the forcedTermination "fault handler". ________________________________ From: Satish Thatte Sent: Tue 10/5/2004 9:53 PM To: Chris Keller Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example I imagine that your idea is that an event would only be delivered to the (implicitly or explicitly) named scope that is completed. Intermediate scopes would be summarily completed without any handlers. ________________________________ From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Tue 10/5/2004 2:09 PM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example Satish, Right, we would still need the semantics you have described for <complete/>, this proposal was just an amendment to your proposal. The <complete/> would still execute the termination of concurrent activities (which won't terminate the scope as that causes a termination event). The scope would then complete at which point the completion event takes place. If the user executes <complete name="cancelOrder"/> then when the complete takes place the additional name field would be made available to the event processing. That way <eventHandlers><onEvent type="completion" name="cancelOrder"> ... </onEvent></eventHandlers> would execute. The decision on which event handler to call would have a precedence order like fault handler/catch... I guess the main thing I am thinking about here is making greater use of the event handler mechanisms where possible and not creating new scope areas. In the future this mechanism could be extended for user-defined event types, those types could be used for intra-process messaging/signaling :). Although I don't think we should go that far in this version of the spec. - Chris -----Original Message----- From: Satish Thatte [mailto:satisht@microsoft.com] Sent: Tuesday, October 05, 2004 3:06 PM To: Chris Keller Cc: wsbpeltc; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example I am still missing something. If <complete/> just generates an event, then it doesn't complete the scope -- or do you mean that it does all of the things like terminating concurrent activities that we talked about earlier but instead of a completion handler we have an event handler that can "subscribe" to this event? Will think about your named completion ideas some more. -----Original Message----- From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Tuesday, October 05, 2004 11:43 AM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example Satish, No, I don't mean we add a complete activity that gets called in the event handler, not sure how you read that in what I said. My thinking is instead of adding new top level handlers to scopes we add new event types, which can be listened for in the scope/eventHandlers container. In terms of completion handling my thinking was that scope completion always happens when no fault is thrown. In the new case it is triggered explicitly by the addition of your new activity <complete/>. Whether or not someone cares about the actual event which is generated by the completion is a different story. That is what is addressed by your completionHandler and my proposal to have completion be an event. Named completion could be accomplished by the addition of a message or name attribute attribute to the complete activity you have suggested such as <completion message="..."/>. Then we use the either use the matching mechanism of the message and event handler for the named type of event (i.e. completion in this case), since <onEvent> already includes an attribute to receive a message. Or we add a new kind of matching for named events of a type (e.g., <onEvent type="completion" name="myname"/>). - Chris -----Original Message----- From: Satish Thatte [mailto:satisht@microsoft.com] Sent: Tuesday, October 05, 2004 2:16 PM To: Chris Keller Cc: wsbpeltc; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example But how would the event handler force completion? Do you mean we add a complete activity that gets called in the event handler but only completes the scope the handler is attached to? IOW no completion handler and no named completion? -----Original Message----- From: Chris Keller [mailto:chris.keller@active-endpoints.com] Sent: Tuesday, October 05, 2004 7:14 AM To: Satish Thatte Cc: 'wsbpeltc'; ygoland@bea.com Subject: RE: [wsbpel] Re: completionHandler example Satish, I am also unsure of the point of failure to which you are eluding, but in general support some of the concepts you are proposing. I would suggest a change to your recent proposed additions, completion and termination handlers, to make it easier to add potentially more in the future (e.g., finally and user-defined events), without the introduction of new elements. I suggest that we change the onEvent mechanism to deal more generically with event types. The additions you have proposed are essentially events generated by scopes. So the idea would be to allow onEvent to include a type. For example: <eventHandlers> <onEvent type="completion" ...> ... </onEvent> </eventHandlers> The default type could be "message" (or "receive", pick a good name), which is the current usage of onEvent. Thoughts? - Chris -----Original Message----- From: Yaron Y. Goland [mailto:ygoland@bea.com] Sent: Monday, October 04, 2004 8:05 PM To: Satish Thatte Cc: wsbpeltc Subject: [wsbpel] Re: completionHandler example But Satish, that is exactly what my example does. Could you please be more specific in identifying the point of failure? Thanks, Yaron Satish Thatte wrote: > > > That doesn't work if you want to do cascading completions aka named > completions. > > -----Original Message----- > From: Yaron Y. Goland [mailto:ygoland@bea.com] > Sent: Thursday, September 30, 2004 11:17 AM > To: Satish Thatte > Cc: wsbpeltc > Subject: Re: completionHandler example > > I realize why putting the completion handler logic before the complete > doesn't work but why doesn't putting it after the completion handler > work? > > scope > variables > variable name="MessageTrackerVariable"... > sequence > scope wrapper > flow > scope A_end_in_complete_to_wrapper > ... > scope B_end_in_complete_to_wrapper > ... > scope C_end_in_complete_to_wrapper > ... > scope CompletionHandler > (Check MessageTrackerVariable and see if any cleanup is > needed) > > Because the exit point of a completed scope is always well defined can't > > the completion handler logic be placed after the completed scope? > > Yaron > > > Satish Thatte wrote: > > > > > > Yaron, > > > > During the F2F you asked for a completionHandler example. Here is my > > try with some explanations. Please let me know if this makes sense to > you. > > > > > > Satish > > > > > > The completionHandler is the common process logic required at all > points > > of premature completion within a scope. The only difference between > > copying it just before each occurrence of a <complete/> activity thus > > > > > > > > <sequence> > > > > <completionHandler logic> > > > > <complete/> > > > > </sequence> > > > > > > > > and the proposed completionHandler feature is that the > completionHandler > > logic executes *after* termination of all activities in the > prematurely > > completed scope. Thus it is a pure macro if the prematurely completed > > > scope does not contain concurrent activities. Many examples of the > use > > of premature completion, e.g., completion of N out of M activities in > a > > flow, do involve concurrency. Consider a case where M suppliers had > > been contacted concurrently and the process was waiting for > asynchronous > > responses (forgive the use of the word :-)) from them. After at least > N > > of them send responses the scope completes. Suppose the conversation > > with each supplier is wrapped in a scope and a terminationHandler is > > used to inform a supplier whose conversation was forcibly terminated > > that their response is not needed. But perhaps we did not or could > not > > ensure that *exactly* N replies arrive because the race was too tricky > > > to control. Thus it is possible that more than N responses arrived. > > The completion handler could detect this situation, pick the N we > really > > want and inform the rest that their responses have been rejected so > that > > we exit the scope cleanly with exactly N accepted responses. > > > To unsubscribe from this mailing list (and be removed from the roster of the OASIS TC), go to http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr oup. php. To unsubscribe from this mailing list (and be removed from the roster of the OASIS TC), go to http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr oup. php. To unsubscribe from this mailing list (and be removed from the roster of the OASIS TC), go to http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr oup. php. To unsubscribe from this mailing list (and be removed from the roster of the OASIS TC), go to http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr oup. php. To unsubscribe from this mailing list (and be removed from the roster of the OASIS TC), go to http://www.oasis-open.org/apps/org/workgroup/wsbpel/members/leave_workgr oup. php.
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