[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: csp as database query language

Gordon Hutchison wrote:

Do you mean something analogous to the "ready set" for a process - i.e.
those events the process will
accept from it's environment being the result set of the query processed at
that point?

I was often warned that visibility of the offered events of a process
without them actually
occurring led to a break down of some of the useful mathematical properties
of composed CSP
processes. Can anyone (re)explain this to me....  :-)

I am not sure who said that and in what context. But I plan to give a paper at CPA-2003 provisionally called "Overtures and hesitant offers". That is all about the semantics of hiding and offered events not actually accepted (in my denotational terminology). The point is that a CSP(P) process can undergo internal transitions as a result of an offer, even if the offer is not accepted.

The laws of hiding ("strong hiding" as opposed to "ordinary hiding") depend on whether you include such "overtures". In almost all realistic circumstances, "overtures" should be included. Perhaps that comment was picking up on the difference between the two sets of laws?