Steven Legg wrote:
>
> Egon,
>
> Egon Andersen wrote:
> > Steven Legg wrote:
> > > 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]
> >
> > I believe all your problems boils down to and is solved by:
> >
> > 18.11 Within an instance of value notation for an integer type with a
> > "NamedNumberList", any occurrence of a name
> > that is both an "identifier" from the "NamedNumberList" and a
> > reference
> > name shall be interpreted as the "identifier".
> >
> > 19.10 Within an instance of value notation for an enumerated type, any
> > occurrence of a name that is both an
> > "identifier" from the "Enumeration" and a reference name shall be
> > interpreted as the "identifier".
>
> The key point is that without the TYPE parameter being instantiated it
> is not possible to decide whether the foobar after the DEFAULT is both a
> reference and an identifier (from a NamedNumberList or an Enumeration,
> in which case we will assume it is an identifier), or just a reference.
> So whether foobar is ultimately an identifier or a reference depends
> on the actual parameter for TYPE in any reference of Foobar.
>
> For convenience, here's that type definition again.
>
> Foobar { TYPE, TYPE:foobar } ::= SEQUENCE {
> field1 TYPE DEFAULT foobar,
> field2 INTEGER { first (foobar) }
> }
>
> In general, if I don't know whether a name is a DummyReference then I can't
> make definitive judgements about questions like "is the DummyReference
> employed at least once within its scope ?" and "is the usage of the
> DummyReference consistent with its syntactic form ?" just by looking at
> the parameterized definition in isolation. I can only answer those questions
> during the process of actually expanding out specific parameterized
> references
> (and the answers can be different depending on the actual parameters).
> So I suppose my question is: is ASN.1 parameterization meant to be this way
> ?
>
> Regards,
> Steven
Hi Steven,
I can see now that there were more to it than I saw at first.
As I see it, it is a bug i X.683.
I think you have pointed out several problem in X.683 and I hope the
ASN.1 group will dig deep into solving this in a consistant way.
Best regards
Egon Andersen
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