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Subject: Re: [wsbpel] Example for how compensation relates to WS-T (BA)
Suppose you have some process A that performs some operation and supports compensation through its process-level compensation handler. (The topic of discussion is process-level compensation handlers, not scope-level compensation handlers, which are covered in the appendix) You have some process B that performs an activity called X. Activity X invokes process A and so process B may later on decide to invoke A's compensation handler. Assume you would want to use WS-TX to do that. Interoperability means that two systems would understand how it works and do it in the same manner (barring any other differences). What would the compensation handler for activity X look like? Let's say A is never compensated unless there is a compensation handler for activity X. The compensation handler for activity X does not need to do anything, so it contains an <empty> activity. According to the current spec, if the compensation handler includes an <empty> activity then nothing would happen. So there needs to be a clarification that some work would indeed happen and that this compensation handler may actually throw a fault (if A returns 'faulted'). Another implementation may decide that to compensate A you need to invoke the default compensation handler for X. So if X has a compensation handler containing <empty> it would not invoke A's compensation handler, but if it has no compensation handler then A gets compensated using WS-TX. You can use the <empty> activity to prevent A from being compensated (a good thing), but you can't interact with A within X's compensation handler, which violates the need to pass data to a compensation handler. Another possibility is for X's compensation handler to explicitly send a compensation message to A. Unfortunately, X doesn't know the participant or coordination addresses and so can't pass them to A's WS-TX implementation. Considering the lack of clarification in the specification I am very curious to see what such an example would look like. arkin Edwin Khodabakchian wrote: >I suggest that we take one of the examples used by Satish in the F2F (travel >procurement) and try to get down into the details of how exception >management and compensation management would be implemented. This will help >us flush out the details of how BPEL and WS-Transaction (BA) work together. > >If we decide that this is valuable, I volunteer to implement the BPEL >processes once the use case has been agreed on. > >Thoughts? > >Edwin > >
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