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- From: "Peter Jacobi" <pj@walter-graphtek.com>
- To: Olivier.Dubuisson@francetelecom.fr
- Date: Thu, 22 Jun 2000 16:09:33 +0200
Olivier, All,
> > a) use the tags as element names ("A17" for [APPLICATION 17]),
> > use fixed attributes for identifiers and data type names.
>
> Tags are historical "residues" in ASN.1. They are only used by the
> BER encoding rules.
> It is now recommended to add the "AUTOMATIC TAGS" clause in the
> module headers and to not take core of the tags any more.
Even when AUTOMATIC TAGS is used, each element has a tag.
And there seems to be an argument for tags, as can be seen by the wide
selection of file formats using some sort of tagging, to be extensible (e.g.
MPEG).
> > b) use the identifiers as element names, use fixed attributes for tags
> > and data type names.
>
> What's the need to keep the tags and type names? It seems to me that
> this verbosity is useless.
In the normal case, no verbosity is involved, as fixed attributes aren't
transmitted in the document instances.
> Do you make the assumption that both sides (i.e., the encoder and the
> decoder) are generated from the same ASN.1 module?
Yes, but I want to be prepared for extensions. That's the main reason
you cannot drop the tag, as that would prohibit round-tripping BER-
>XMLencoding->BER.
The original sender may use a special tag value to insert an element into
a SEQUENCE. You must keep this tag value in the XML encoding for the
sahe of re-producing a BER encoded version.
Regards,
Peter Jacobi
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