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> -----Original Message-----
> From: Mike Champion [mailto:mc@xegesis.org]
> Sent: Saturday, September 14, 2002 07:25
> To: XML Dev
> Subject: Re: [xml-dev] [Fwd: Re: The 11-pound solution (fwd)]
>
>
> 9/13/2002 5:19:56 AM, "Alaric B. Snell"
> <alaric@alaric-snell.com> wrote:
>
>
>
> >
> >So how about we stop trying to [ab]use XML for data and just
> bind an XSLT
> >engine to a nice XER (http://asn1.elibel.tm.fr/xml/) codec,
> if you REALLY
> >want XSLT
>
> Beccause throwing hardware at the problem is so much cheaper?
> Because the
> network effect favors generic, inefficient technologies over
> specialized, efficient ones?
>
> <pontification flame-bait="true">XML is worse than ASN.1 for
> network protocols.
> Worse is better. Deal with it.</pontification>
>
Mike,
Comparing XML with ASN.1 is fundamentally meaningless.
ASN.1 is a language that describes the information content of messages.
The user of ASN.1 is a person who writes or reads an ASN.1 data
description module, whereas the user of XML is usually a machine that
interacts with another machine. Most likely, the human users of an
application never see a piece of XML being produced and consumed within
the application. On the other hand, ASN.1 modules are produced by human
beings, published in standards or other such, and used by the
implementers of these standards.
Given this, what is the meaning of "XML is worse (better) than ASN.1
for network protocols"?
ASN.1 does allow use of XML in the actual messages: XML is one of the
possible representations of data in ASN.1 (the others being the
traditional binary encoding rules BER/DER/PER). XER, as mentioned by
Alaric, means the use of XML to encode data described in ASN.1. A basic
form of XER has been standardized by the ITU-T and ISO JTC 1 (X.693),
while an advanced form of XER (named VXER) is about to be approved.
ASN.1 with VXER is a powerful XML schema definition language.
The ITU-T and ISO JTC 1 are also developing a recommendation (X.694)
which provides a full mapping from XML Schema into ASN.1 + VXER. This
mapping allows any XML Schema schema to be translated into ASN.1 (in a
fixed way). The resulting ASN.1 will be describing the same XML
documents as the original XML Schema, thus allowing the use of tools
based on either language on any of two communicating endpoints,
guaranteeing interoperability and extending the range of possible
applications. Among other things, this allows exploiting the binary
encoding rules of ASN.1 to save bandwidth and CPU cycles wherever this
makes sense.
Alessandro Triglia
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