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Subject: Re: [bt-spec] BTP Issue 53 : will or may contradict ?


 
 
Yes, assuming the CONFIRMs are sent out synchronously, waiting for the replies. That's not necessarily a good idea - if the first is slow to respond, the others have to hang on waiting to know the otucome. That might be ok in a closed environment, but would seem to be more iffy in the "more loosely coupled" environment we expect for BTP.
 
"may" makes the statement rather too weak - it really is a very special case that an wrong autonomous decision doesn't produce a contradiction.
 
Suggestion: just add "usually" in "latter will usually cause a CONTRADICTION"
We should not be assuming anything about the environment in which BTP will "typically" be used. As a result, it's not an objective statement to say it's a "very special case", since that in itself is based on certain assumptions about deployment. I don't mind "usually", but what I do want is some text along the lines of:
 
"If the coordinator is issuing the second phase of a successful (i.e., CONFIRM) completion protocol synchronously, then it is possible upon the receipt of a CANCEL message from the first non-RESIGNED participant for the coordinator to change it's decision to CANCEL the atom, and in such a way prevent a CONTRADICTION from occurring. Otherwise ..."
 
I would like to avoid contradictions as much as possible, because cleaning up after them is going to be a nightmare for system administrators, especially if they are spread across the planet. It's exactly the same argument as for this kind of optimisation in TPs with heuristics.
 
Mark.
 
----------------------------------------------
Dr. Mark Little
Transactions Architect, HP Arjuna Labs
Email: mark@arjuna.com | mark_little@hp.com
Phone: +44 191 2064538
Fax  : +44 191 2064203
 
 


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