"Egon Andersen, Talura" wrote:
>
> Steven Legg wrote:
> >
> > Folks,
> >
> > In trying to tie up some loose ends in my ASN.1 compiler implementation
> > I've come across some situations where the interplay between
> > parameterization
> > and ambiguity in the notation becomes problematic. The ASN.1 specifications
> > don't provide sufficient detail for me to determine how to resolve the
> > problems.
> >
> [snip]
> X.683:2002 8.4 do have a note on this too.
>
> > --------------------------------------------------------------------------
> >
> > Consider this type definition:
> >
> > Foobar { FOOBAR } ::= SEQUENCE {
> > field1 [1] INTEGER (CONSTRAINED-BY{ FOOBAR })
> > }
> >
> > It isn't possible to decide whether FOOBAR is an information object class or
> > a type from the type definition alone. It can only be determined when
> > Foobar is referenced with actual parameters.
> >
> > Should such an ambiguous assignment be rejected outright, should it be
> > disambiguated by its first usage, or should all references with either a
> > type or a defined object class as the actual parameter be allowed ?
> >
> > Regards,
> > Steven
>
> This part wasn't addressed by my previous reply and I haven't been able
> to find a 'solution' to the problem in the standards.
> Maybe this is a candidate for a defect report?
>
> PS. It is CONSTRAINED BY, not CONSTRAINED-BY.
>
> /Egon
To solve this problem and some other difficulties with parameterization,
where the parameter is a DefinedObjectClass, I would suggest a change in
the definition of Parameter, so that DefinedObjectClass should be
preceded by "CLASS" ":".
(Allow ParamGovernor to be "CLASS" in this case and change X.683 clause
8.3 a) to reflect this.)
This would also remove the need for the NOTE in X.683 clause 8.5.
This would make it easier for a human reader to understand and it would
also make it easier to make compiler support.
The only drawback I see is that protocols using DefinedObjectClass in
parameterization, should be updated, but that is no big problem.
Best regards
Egon Andersen
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