RE: Priority modeling with CSP?

["Gerald Hilderink" <g.h.hilderink@xxxxxxx>]

Dyke,

Please, read a paper I wrote, titled "Conditional Communication in the
Presence of Priority" CPA 2000 (or WoTUG-23). This paper discusses the
PRI in PRI PAR and PRI ALT. It discusses a different ALT and PRI ALT
implementation for dealing with priority. This includes priority
inversion problems and solving them. We had to modify these ALTs to make
them more efficient in the presence of the PRI PAR. These ALTs, use of
output guards, and buffered channels overcome (or solve) priority
inversion in many ways. CTJ contains these implementations. 

Priority inheritance is not possible with channels. Priority inheritance
is not a very good idea at the first place; it is unnatural and
indicates a bad design. 

Priority is just a solution to guarantee better performance under
real-time constraints with shared processor-time (interleaving
semantics). It is easy to abstract away from the semantics of these PRI
constructs to CSP operators. The CSP descriptions in the paper is not
very strong, but helpful to see the meaning of "preference priority".
Priority in this paper is related to events rather than to processes or
active objects. IMHO, inheritance of processes should not include
inheriting priority or whatsoever, since priority is a relationship
between two processes and a process has no knowledge about priority in
the same way as a process has no knowledge about the existence of other
processes. Priorities and threads as use in object-orientation are NOT
object-oriented, whereas our approach is process-oriented, thus very
object-oriented.

Gerald.

> -----Original Message-----
> From: G.S.Stiles [mailto:dyke.stiles@xxxxxxx] 
> Sent: donderdag 24 januari 2002 7:12
> To: occam/csp list
> Subject: Priority modeling with CSP?
> 
> 
> Greetings:
> 
> CSP does not include priority itself, but has it been used to 
> model schemes for handling priority inversion, priority 
> inheritance, etc.???
> 
> Dyke.
> 
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