Re: XML schema and RDF datatypes [was: comments...]

From: Dan Connolly (
Date: 10/02/01

"Peter F. Patel-Schneider" wrote:
> > [Dan Connolly]
> > >It's also possible to design a language where the type of
> > >a literal may *depend* on a declaration from an XML schema:
> > >
> > >     <kr:KRLang xmlns:rdf=""
> > >             xmlns:ex="http://example/vocab">
> > >     <ex:Person>
> > >       <ex:name>John Doe</ex:name>
> > >       <ex:shoeSize>10</ex:shoeSize>
> > >     </ex:Person>
> > >
> > >so that the "10" above is not a logical constant at all;
> > >not until you find a/the schema for http://example/vocab
> > >do you know how to parse/interpret "10"... i.e. the
> > >meaning of that chunk of XML is dependent on all the
> > >trust issues around following links from one document
> > >to another (not to mention a complete implementation
> > >of XML Schema, an effort several orders of magnitude
> > >larger than an RDF 1.0 parser).
> > >
> > >This sort of language is not a candidate for a future
> > >version of RDF: it fails to meet
> > >one of the basic requirements of RDF: that an RDF document
> > >stands on its own as a logical formula.
> I fail to see how this follows.

I'm not sure I can explain it any better. Maybe Pat H. can;
he seems to have understood.

> I would also appreciate a pointer that provides some measure of support for
> the premise of this inference.  (In fact, I would find it very instructive
> to see a concise, authoritative enumeration of the ``basic requirements of
> RDF''.)

Er... I'm not sure what sort of authority you're after.
The RDF Model & Syntax WG didn't make requirements part
of the 1.0 spec.

This excerpt is from a NOTE that has no formal standing,
but perhaps you'd find it convincing regardless of the source...

Lack of ambiguity 

Some programming languages allow one to introduce identifiers
from new name spaces in such a way that it is not possible to
know which namespace a local identifier belongs to without
accessing both the module interface specifications and checking
which one has with the highest priority, or  most recently in the
document, redefined a given local identifier. 

This may have some uses in a programming language such as
Java[Java], but it has a serious flaw in that when one module
changes (without the knowledge of the designers of the other
module), it can unwittingly redefine a local identifier used by the
second module, completely changing the meaning of a previously
written document. Clearly, in the Web world in which modules
evolve but documents must have clearly defined meanings, this is

--        Web Architecture: Extensible languages
W3C Note 10 Feb 1998 

Perhaps you would find a statement from one of the RDF 1.0 editors

	"This is indeed an explicit a design decision ..."
	-- Ora to www-rdf-logic Mon, 01 Oct 2001 04:28:11 -0400

As to concise, I condense the design principles of RDF
as follows when I present it:

Semantic Web

     terms grounded in URI space 

     simple XML usage for use with XSLT etc. 

     explicit translation to statements 
         natural language statements 
         logical formulas 

Dan Connolly, W3C

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