RE: CSP-OZ Backtracking.

["Campbell, John" <John.Campbell@xxxxxxxxxxxxxx>]

	Hi

> I am trying to implement an kind of backtracking the CSP comunication,
> like
> 
It sounds like you want a CSP in which a process may engage
in an event speculatively, hoping that the other processes will
eventually confirm their participation.  If they in fact decline, then
the invalidated event would have to be rolled back.

I don't know of such a CSP theory, maybe one of the theoretical types
could comment.  But it seems like you could define such a theory.
Perhaps you could come up with a set of re-writing rules which
compile "tentative" events into sets of events of the conventional
variety.

For example, if you wanted, say one level of (the compiler types
would say) look-ahead, the tenatative CSP processes

	P  ||  Q  Where P= (A [] B])      and Q=  A < some_condition >C

might speculatively allow P to transition to A based on the *hope* that
Q will choose A.  If the some_condition term evaluates to TRUE, the
the transition would become, in some sence "real".  But if it evaluates
to FALSE, then P would have to backtrack back to the alt and engage
in B.  You could get this kind of behavior by re-writing the processes
as:

          P=  (A1 -> (A2 [] (C1 -> B))) [] B

and   Q= (A2 < some_condition >C1)

Where A1,A2 are drived from A, C1 from C.

I suspect that for some pre-determined level of look-ahead, re-writing
rules could always be derived.......If its not already invented, maybe it 
should be.
-jc