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

URIs as names (was: What do the ontologists want)

From: Larry Masinter <lmnet@attglobal.net>
Date: Sat, 19 May 2001 17:11:08 -0700
To: <www-rdf-logic@w3.org>
Message-ID: <NDBBKEBDLFENBJCGFOIJKEBNEPAA.lmnet@attglobal.net>

# Chimpanzees and gorillas can use names like this; so 
# what is all the fuss about? Which makes me think that this can't 
# really be what is meant by a URI. But I still don't know what else 
# there is to the notion.

reductio ad absurdum doesn't really help here. Personally,
I think the fuss is just because people haven't figured out
how the mystical power of the URL turned improverished hypertext
into the multi-billion-dollar World Wide Web.

The use of URIs in RDF and as XML namespace names to identify
things other than network resources is a bit of semantic extension
that doesn't work all that well. You can certainly imagine
defining a URI scheme that would work to name a grain of
sand on a Pensacola beach, but is it really a good idea to
do so? It's kind of like using Goedel numbers instead of
equations.

The simplest way I have of coping with all of this is to note
that URIs (as defined by RFC 2396, at least) are just syntax,
a protocol element that derives having semantics almost entirely
from the context in which it is used. (Early drafts of RFC 2396
were titled 'syntax and semantics', and 'semantics' was dropped).
A URI used in a HREF of an A element in a HTML web page has one
meaning, based on the expected behavior when the link is clicked;
the same URI used as a namespace name in an xmlns attribute has a
different meaning, because it is not expected to be "clicked".
RDF supplies yet another context, but currently isn't clear about
what it intends the meaning of the URIs within it to be.

Part of the problem is that there's a lot of sloppiness about the
level of quoting or indirection. Some RDF statements seem to be
about the actual resources that a Uniform Resource Identifier
identifies, and others are about resources that are merely
described or correlated with those other resources. Getting
the level of indirection right is hard; we haven't been explicit
about when EVAL is called.

Larry
-- 
http://larry.masinter.net
Received on Saturday, 19 May 2001 20:12:14 GMT

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