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   Re: [xml-dev] ASN.1 is an XML Schema Language (Fix those lists!)andBinar

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Bancroft Scott wrote:
> Robin Berjon wrote:
>> The ASN.1 equivalent of a simple XML parser in terms of universality 
>> would have to properly decode (and likely handle negotiation for) BER, 
>> PER, CER, DER, XER, and probably LWER, OER, and SER. That's a bit of a 
>> behemoth to implement!
> Not at all.  While it is possible in theory to create an application 
> that uses all of BER, PER, DER, XML, etc., with very rare exceptions 
> applications use just one of these.  Even in the case where one is using
> an ASN.1 tool that supports all these encoding rules, an application would
> select only those libraries that are needed.

You're missing the point, the operative word being "universality". An 
XML parser can successfully read anything produced based on an XML 
schema language (not to mention all that can be done without any schema) 
-- unless that schema language is ASN.1 (which could be an argument for 
saying it isn't exactly an XML schema language).

If all you have is an ASN.1 schema, and you're on the receiving side, 
you don't know what you're going to get. If it's an ER you don't know 
about you won't read it. That just won't happen if you're using XML. You 
can chose to consider this unimportant, but a lot of us XML folks think 
it is a core asset.

IIRC there was a good passage in Olivier Dubuisson's ASN.1 book about 
how a decoder must know so much, unfortunately I can't find it right now.

> By the way, LWER, OER and SER are not standard encoding rules of ASN.1.
> LWER was a proposal from about a decade ago that was withdrawn by the
> submitter before being progressed.  OER was created in the automotive
> community but did not catch on.  This is the first that I am hearing
> about SER.

Yes I know, which is why I set them aside in the list. SER (Specific 
Encoding Rules for signalisation) is an FT and Nokia joint spec and 
operates things like RNIS and GSM. It is not unrelated to the old work 
on MBER.

Robin Berjon <robin.berjon@expway.fr>
Research Scientist, Expway      http://expway.com/
7FC0 6F5F D864 EFB8 08CE  8E74 58E6 D5DB 4889 2488


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