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Re: Objects, processes, and encapsulation
Hi Tom, Ian, Peter, others,
Too bad I missed the conference...
I read Tom's article. It is a very good start!
The Callback problem can be simplified to something like this:
"During a call to an external object, any method of the
original object may be called from externally. The
state of the original object may therefore have completely
changed during a single method call."
The callback results in a cyclic call, which causes the problem.
Note that in CSP, such cyclic calls would typically result in deadlock.
A sends message to B, and waits for response.
B sends request to A.
Deadlock: A is waiting for the result, and cannot handle
the request sent by B.
Cyclic & Synchronous relationships are a problem: in CSP and in OO.
Should they be rulled out? If so, how? If not, how should they be dealt with?
Marcel Boosten | Philips Medical Systems
System Designer 3D-RA | Room QJ1309
System Design & Image Quality | P.O. Box 10000
Cardio Vascular Development | 5680 DA Best
Marcel.Boosten@xxxxxxxxxxx | The Netherlands
Phone: +31-40-27-69019 | Fax: +31-40-27-65650