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Subject: Re: [wsbpel] Issue - 166 - Does atomicity in assign imply variablelocking?
my personal interpretation of andrew's comment was that locking and atomicity are orthogonal, in which andrew and i violently agree on ;-) Yaron Y. Goland wrote: > So you are asserting that by defining assign as atomic we prevent the > case I described? > > If so then you and Danny are in violent disagreement. > > Yaron > > andrew.francis@mail.mcgill.ca wrote: > >> >> >> Hello Yaron: >> >> >You assert that variable locking is irrelevant to the BPEL >> >>programming model. >> I am "asserting" that one does not need to resort using >> variable locking to describe the atomicity of assignment. >> >> >I don't understand how this assertion can be defended >> >given the example >> <http://lists.oasis-open.org/archives/wsbpel/200409/msg00361.html>.> >> >If there is no variable locking then it is possible for the >> >>assign statements in the example in the linked message,>lets call >> them A and B, to execute as follows: >> >> > Assign A - Read in counter value >> > Assign B - Read in counter value >> > Assign A - Increment counter value and write >> > Assign B - Increment counter value and write >> >> Sorry I don't agree with this statement. You are not >> describing an atomic operation: atomic operations are >> indivisible. Since assign is atomic, then I feel the >> following is a more accurate, but simplified description >> of what happens: >> >> Assign A - Read in counter value. Increment counter value >> and write.Assign B - Read in counter value. Increment counter value >> and write. >> > If we don't specify that assign requires isolation semantics >> >> I think atomic assign operation is much more of an issue >> .... and a challenge for the BPEL engine implementer. >> BPEL engine implementers probably won't have the luxury >> of dealing with data structures that have support from >> atomic operations in a lower layer (i.e., the hardware). >> >> Cheers, >> Andrew >> >> > > 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_workgroup.php. > > >
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