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

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Robin Berjon wrote:
> Alessandro Triglia wrote:
>> Amelia A. Lewis wrote:
>>> We believe in unicode and concrete syntax.
>> Good.  So you don't believe in schemas.  That's fine.  Just use XML 1.0.
> I don't think that that happens to be what Amy said (apologies if I 
> presume wrong). The fact is that at this point in time any schema 
> language for XML defines one single concrete syntax. And a fair part of 
> what the ASN.1 people do not seem to understand is that the XML folks 
> see that as a *good* thing.
> 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!

Nah, just BER. BER is the Basic encoding after all - any general ASN.1 
tool will handle BER; the others are more optional.

This really comes down to application profiles - IIRC, in the original 
use of ASN.1 as Layer 6 of the OSI stack, everyone HAD to support BER 
and could optionally support others.

Although when people define a data structure in ASN.1 and then say "It 
must be encoded in PER", they then choose not to require their parsers 
to support BER - that's up to them, of course.

But in any situation where more than one transfer syntax is allowed, BER 
should be one of them...

Also, it's not as much of a problem as you imagine having all those 
different sets of encoding rules - since the code for each of them 
really only needs to be written once as part of the toolkit; from there 
on up, everything else can be syntax-agnostic.

XML is even worse than ASN.1 in this respect, of course; XML is based 
upon "text", and there are myriad ways of representing this.

An XML parser needs to understand (IIRC) US-ASCII, UTF-8, and UTF-16 or 
something like that, so it could well barf on something written in 
EBCDIC. So a truly universal XML parser really ought to support every 
encoding listed under:


XML is *not* a concrete syntax in terms of actual bytes on the wire, by 
any stretch of the imagination; it's concrete in terms of *characters*, 
but those "characters" are still abstract things in terms of bits on the 

Anybody who is looking for a single concrete syntax ought to leave XML 
alone right now and try XDR (RFC1014; http://www.faqs.org/rfcs/rfc1014.html)



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