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Re: Input sought on datatyping tradeoff

From: Jonathan Borden <jonathan@openhealth.org>
Date: Mon, 15 Jul 2002 09:21:46 -0400
Message-ID: <004401c22c02$9252c590$0201a8c0@ne.mediaone.net>
To: "Drew McDermott" <drew.mcdermott@yale.edu>, <www-rdf-logic@w3.org>

Drew McDermott wrote:

>
> I know it is futile to make the point at this late date, but the whole
> farcical question stems from the fact that RDF (and XML, and SGML, the
> whole ridiculous lineage) have no syntax for string literals.  If
> everything is a string, then nothing is a string.  The problem could
> be solved very simply if every literal found in an RDF file belonged to
> at most one literal class (some apparent literals being ill-formed,
> and hence not belonging to any).  That would require strings to be
> indicated in some explicit way.  Hey, about quotes?

I understand your arguments but you are not giving SGML nor XML a fair
evaluation.

SGML has mandatory schema (called DTD) which is capable of assigning
unabmiguous datatypes to essentially every syntactic structure ... such
facilities are called NOTATIONs, Groves as well as an ability to specify
delimiter characters (e.g. '<' and '>' are not intrinsically 'special' as
far as SGML is concerned).

SGML has had success in specifying precise documentation systems at very
high expense for very large customers. XML was conceived as an attempt to
_simplify_ SGML for mass market use and to some extent it has succeeded
(mass market use, but not simplification :-))

So there are lots of facilities in both SGML and XML that have not achieved
widespread use (e.g. NOTATIONS).

Now XML Schema has been introduced to 'make up' for the shortcomings of XML
in regard to datatypes in the absense of NOTATIONs and DTDs.

If one _requires_ an XML Schema (or a RELAXNG schema for that matter), one
can simply and unambiguously have _datatypes_ in XML documents. Such
datatypes are delimited by markup not quotes -- no biggie.

e.g.

<ex:foo xsi:type="xsd:integer">10</ex:foo>

Now you may not like the syntax, nor like XML Schema, but let's not argue
about that because it is _another argument_. The _problem_ is not that XML
has ambiguous syntax rather that _the type of XML_ that RDF uses does not
adequately provide for such syntax. Namely RDF and XML Schema are not
entirely compatible, e.g. it is not possible to write a complete RDF syntax
specification using XML Schema etc.

...
>
> Only because of XML absurdity, which has carried over to N3.
...
>
> I'm sorry to indulge in a bit of sarcasm here and there, but the
> persistent desire of the Web community to shoot itself in the foot
> over this issue, nay, saw its foot off inch by bloody inch, baffles
> me.

Well, the problem is that _different parts_ of the Web community are going
off and doing incompatible things, e.g. the 'solution' that XML Schema has
come up with is not entirely compatible with RDF, and there are many many
other examples of such issues. But that is life I suppose.

I suggest that RDF drop this issue for the moment, because a _proper
treatment_ will likely require changes to the RDF syntax (as Drew points
out) which would be most appropriately done in RDF 2 (during which RDF 2 and
XML Schema 2 could be properly aligned for example)

Jonathan
Received on Monday, 15 July 2002 09:36:36 GMT

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