"Egon Andersen, Talura" wrote:
>
> Olivier Dubuisson wrote:
> >
> > "Egon Andersen, Talura" wrote:
> > >
> > > Hi,
> > >
> > > I came across the following notation:
> > >
> > > MyType1 ::= SEQUENCE {
> > > ...,
> > > ...}
> > >
> > > This seems to be perfectly legal according to X.680 (1997 E) clause 24.1
> > >
> > > According to 3.8.29 the 'extension insertion point' is in between the
> > > two ellipsis.
> > >
> > > MyType2 ::= SEQUENCE {
> > > ...,
> > > alpha INTEGER,
> > > ...}
> > >
> > > should then be the propper way to extend with a NamedType.
> > >
> > > But this does not comply to any of the alternatives in
> > > ComponentTypeLists.
> > > All alternatives in ComponentTypeLists requires a RootComponentTypeList,
> > > which is non-empty.
> >
> > Good catch! I'll make sure that this will be mended in the 2002 edition of
> > the ASN.1 standard.
> >
> > > How do I extend MyType1 according to X.680 (1997 E)?
> > >
> > > In the X.680 (1994 E)/Amd.1(1995 E) the notations would have been:
> > > MyType3 ::= SEQUENCE {...}
> > > and extended to:
> > > MyType4 ::= SEQUENCE {..., alpha INTEGER}
> >
> > Correct. You can use it, for it's not worth having a second extension marker
> > when the extension root is not splitted in two parts. Anyway 24.1 needs to
> > be mended.
>
> Yes, the above is valid X.680 (1994 E)/Amd.1(1995 E) syntax, but any
> fully X.680 (1997 E) compatible compiler will make a syntax-error on
> this construction!
> So we actually also lost backward-compatibility!
> (I've sent a defect report on this.)
My brain is mainly occupied with the organization of the ASN.1 meeting here
in India. That may be the reason why I don't understand where's the lost of
backward-compatibility.
Also please send your defect report to me so that I can make sure that
it'll be addressed in Bangalore.
--
Olivier DUBUISSON
france telecom R&D
_ DTL/MSV - 22307 Lannion Cedex - France
( ) tel: +33 2 96 05 38 50 - fax: +33 2 96 05 39 45
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