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Eric van der Vlist wrote:
>
> On Mon, 2003-11-03 at 17:37, Michael Champion wrote:
>
> > Sounds like SGML circa 1996! Maybe it's time for a serious
> refactoring
> > of ASN.1 to find the 80/20 point in there. Maybe ASN.2
> could be to
> > ASN.1 what XML is to SGML.
>
> Another reason why I'd compare ASN.1 to SGML rather than XML
> is that, like SGML, ASN.1 seems to be schema centric: it
> looks like you can't do anything in ASN.1 without designing a
> schema first like you can't do much with SGML without
> designing a DTD first.
>
> Since the breakthrough of XML versus SGML is the fact that
> schemas are now optional, isn't ASN.1 a regression in this respect?
>
> I'd say that this might be a reason why ASN.1 isn't binary
> XML, it would rather be binary SGML!
Since XML 1.0 is now one of the standard "transfer syntaxes" available for
ASN.1, ASN.1 is no longer necessarily "binary", but it is also "XML".
I agree that schemas are now optional. If, in a given application domain,
the specification of a schema (be it done in XML Schema, RELAX NG, or ASN.1)
is impractical (or otherwise not desirable), one can go ahead without a
schema. If a schema is instead seen as practical and useful, then ASN.1 is
now one of the schema languages available.
As has been said several times in this thread, by selecting ASN.1 as the
schema language, you *implicitly* get a number of possible alternative
serializations (encodings): XML, BER, PER, etc. In addition, even if you
start off with an XML Schema schema, by using X.694 you can obtain a
99%-equivalent ASN.1 schema which gives you those alternative encodings. If
you don't need any encodings other than XML, you just don’t select them -
select XML 1.0 as the only encoding for your ASN.1. (And again, if having a
schema is a problem, don’t use ASN.1.) On the other hand, by starting off
with ASN.1, you can enjoy certain features of the language, which makes
ASN.1 useful in its own regard as an XML schema language even for those
application domains that will never need binary encodings.
The main point I wish to make here is that ASN.1 and XML 1.0 are *not*
competing technologies. You can describe ASN.1 as a
"transfer-syntax-agnostic" schema language that comes with several standard
"pluggable" transfer syntaxes, one of which is XML 1.0.
Alessandro Triglia
>
> Eric
>
> --
> Don't you think all these XML schema languages should work together?
>
> http://dsdl.org Upcoming schema tutorial:
> - Philadelphia
> (7/12/2003) http://makeashorterlink.com/?V28612FC5
> Tutoriel XSLT:
> - Paris (25/11/2003)
> http://makeashorterlink.com/?L2C623FC5
>
> --------------------------------------------------------------
> ----------
> Eric van der Vlist http://xmlfr.org
> http://dyomedea.com
> (W3C) XML Schema ISBN:0-596-00252-1
> http://oreilly.com/catalog/xmlschema
> --------------------------------------------------------------
> ----------
>
>
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