Re: DER coding of a default syntax value

[Bancroft Scott <[e-mail]>]

Peter Williams <[e-mail]> 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.