Subject: SDL-News: Priority in Enabling Condition
Date: Mon Mar 17 1997 - 11:21:04 GMT
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-----From Rajesh_Kumar <rajeshk#cadence.com> to sdlnews -----
Please refer to the section about "Enabling condition" in the Z.100 spec of
SDL. It states that ....
"In the case of multiple enabling conditions, these are evaluated
in an arbitrary order before entering the state."
The point, I want to make is that if somehow we can specify the order in
which these multiple enabling conditions will be looked at, then it will
a great deal in simplifying some of the enabling conditions.
As an example look at the following :
/* Assume that i1 is an input signal and
o1, o2, o3 are output signals to the process
dcl Abort, a1_on, a2_on Boolean;
provided ((not Abort) and a1_on);
provided ((not Abort) and (not a1_on) and a2_on);
Here since the order in which the enabling conditions will be evaluated
is not known, so the user has to explicitly write the "(not Abort)" and
"(not Abort and (not a1_on)". Is there any way in which he could have
skipped this explicit specification and written it like the following:
provided ( a1_on);
provided ( a2_on);
This would have been possible say, if some priority could have been
attached with each condition as in Continuos signal, or if there were
a predetermined evaluation order, like top-to-bottom, say.
Thanks and Regards
-----End text from Rajesh_Kumar <rajeshk#cadence.com> to sdlnews -----
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