W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2001

RE: rdf as a base for other languages

From: Peter Crowther <peter.crowther@networkinference.com>
Date: Sat, 2 Jun 2001 13:09:56 +0100
Message-ID: <B6F03FDBA149CA41B6E9EB8A329EB12D05A358@vault.melandra.net>
To: "'Graham Klyne'" <GK@ninebynine.org>
Cc: www-rdf-logic@w3.org
> From: Graham Klyne [mailto:GK@ninebynine.org]
> At 01:07 PM 6/1/01 -0400, Peter F. Patel-Schneider wrote:
> [...]
> >Sure, you can do anything you want outside of RDF.  However, 
> >if you want
> >RDF to represent anything, you better do all your work within RDF.
> 
> Why the insistence on all-or-nothing?  Is there any 
> fundamental reason why 
> we cannot start with a language capable of expressing ground 
> facts, and 
> extend it in a consistent way (creating a new language, "outside" the 
> original) such that the original language for expressing 
> ground facts is present as a sub-language?

The questions here are:

a) whether the original language allows such extensions at all;

b) whether there is a way within the original language of denoting out
what's original versus what's extension;

c) what an agent that only interprets the original language should do with
the extensions.

With RDF as it stands:

- If you posit that the original language allows such extensions because
it's all just triples, then there's no way to denote what is original versus
what is extended and there's therefore no way for an agent that only
interprets the original language to know when its fallen off the edge of a
statement in the original into an extension --- that's fine if everyone uses
the same extension language, but then why is RDF around at all because the
separate layer of RDF is not useful on its own.  So everyone can use (say)
DAML+OIL, but you cannot rely on any information a non-DAML+OIL agent
extracts from that chunk of RDF that uses DAML+OIL because it may make
incorrect assumptions about the extensions: for example, that the relation
petersExtension:negation does (or does not) represent the concept of
negation.

- If you posit that the original language does not allow such extensions,
then there is no way of representing anything other than positive ground
triples and the language is of very limited use.  So you can't create
DAML+OIL on top of RDF, and have to encode it in some other way.

For me, the minimum addition to RDF would be a way of distinguishing
'traditional' RDF positive ground triples from triples that have been
generated as structure by some language outside RDF.  Ideally I'd like to be
able to distinguish *which* language generated the structure as well.

I wonder whether the RDF aficionados are assuming that this is done using
namespaces, and that rdfs:* is the 'original language' and everything else
is an extension?  But if so, the language is even more limited as you cannot
create your own subjects, predicates, and objects; it seems that something
outside the namespace mechanism is required.

		- Peter
Received on Saturday, 2 June 2001 08:10:07 GMT

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