Re: DER coding of a default syntax value

Peter Williams <peter(_at_)verisign(_dot_)com> wrote:

> let me, with my better yet better ASN.1 education now, again reexpress what
> I believe we are saying isnt allowed to be expressed (as the notation
> grammar prevents it):
>
>
>  foo2  EXTENSION ::= {
>        SYNTAX                  PetersBooleanType -- a typereference
>        IDENTIFIED BY           id-foo2
>        }
>
> PetersBooleanType ::= BOOLEAN DEFAULT False
>
> this is because PeterBooleanType isnt legal notation. a typereference to
> "Type" (BOOLEAN) cannot just
> arbtraily assign itself with a default value, only component
> types can do this. The ASN.1 syntax grammer (happily) prevents
> this illegal expression.

Correct, the definition of PetersBooleanType is invalid.

> Ok next nasty. 
>
>  foo3  EXTENSION ::= {
>        SYNTAX                  PeterSeqOfType -- a typereference
>        IDENTIFIED BY           id-foo3
>        }
>
> PeterSeqOfType ::= SEQUENCE OF BOOLEAN DEFAULT {}

This too is invalid, since DEFAULT can appear only in the definition
of a component of a SET or SEQUENCE.

Bancroft Scott
Open Systems Solutions, Inc.