Subject: Alternative approach to discipline defintions and their compatibility and resolution
From: Graham Helwig (ghelwig@asc.corp.mot.com)
Date: Wed Jan 16 2002 - 23:10:12 PST
Hello,
Based on the following paragraph from the "Re: resolveto statement's
discipline list constraint" email (dated "16 Jan 2002") highlights a
double standard within the LRM wrt. the compatibility of base
disciplines of differing domains. Below is a possible approach that may
resolve this situation
> I'm not sure that that is necessary. The 'connect/resolveto' mechanism is
> really just for attribute resolution, and the current ACMI mechanism really just
> converts between views on what is considered (electrically) the same node,
> i.e. continuous (actually piecewise-linear) and discrete (logic) values. It is not
> physically possible to connect nets with different base disciplines such that
> they become one node, so the connect statements above are unnecessary
> because you don't need to do attribute resolution.
From a users point of view the following base discipline compatiablity
statements are true:
"logic" and "cmos" discrete disciplines are compatible
"electrical" and "logic" disciplines are compatible
"mechanical" and "logic" disciplines are NOT compatible
"mechanical" and "electrical" disciplines are NOT compatible
From a language point of view, any base discipline should be
incompatible with each other, therefore the above examples all should be
incompatible with each other. These examples high-lights a double
standard wrt. disciplines and their compatibility rules. After talking
with Sri, the users and language points of view can be made consistent
with each other through the use of derived disciplines (similar rules to
derived natures). For example, consider the following derived discipline
definitions:
discipline voltage;
domain continuous;
potential Voltage;
enddiscipline
discipline electrical : voltage;
// NOTE: The potential binding is inherited.
flow Current;
enddiscipline
discipline logic : electrical;
// NOTE: The flow and potential nature binding
// are inherited but not used.
domain discrete;
enddiscipline
discipline cmos : logic; // Alternatively "cmos : electrical"
enddiscipline
Using this these derived discipline definitions and applying a domain
independent rule that all base disciplines are incompatible with each
other, the above compatibility examples become true again. The
difference now is that the logic of the compatible are contained in the
discipline definitions instead being embedded within the LRM
documentation.
Should discrete discipline definitions be restricted to derive from the
"electrical" discipline definition only?
Note: A side effect of this change is the DR and ACMI mechanism will be
based on the "domain" specification of the two compatible nets being
resolved and not based on their incompatibility.
As a result, we feel that derived disciplines can be efficiently used in
trying to discipline resolution and ACMI in conjunction with the domain
attribute for a discipline. So this approach could be investigated
further to clarify the LRM and associated algorithms, with the
possibility of reintroducing this in the BNF.
Regards
Graham
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