Re: Distributed querying on the semantic web

From: "Phil Dawes" <>
Subject: Distributed querying on the semantic web
Date: Mon, 19 Apr 2004 12:48:02 +0100

> Hi All,
> I like Patrick Stickler's assertion that in order to participate in
> the 'semantic web', http URIs should be dereferencable to some
> information about the URI. 

I believe that you meant information about the referent (denotation, meaning,
...) of the URI.  If all that is available is information about the URI,
then this is not very interesting, as I really don't need to know much
about a URI.

However, I do hope that you did not mean necessary information about the
referent (denotation, meaning, ...) of the URI.  I vigorously oppose any
attempt to require that part of the meaning of a URI that my applications
are supposed to abide by be the meaning that can be found in a document
found by dereferencing the URI.  To pick my favourite example, I do not
want my applications to be required to abide by the information available
at just because I use the URI, *even* if this information is only
something like rdf:type foaf:person .

> I am considering how an infrastructure
> could be built where this could be exploited for distributed queries.
> The main problem with Patrick's concise-bounded-description idea from
> this respect is how to find references to a term. 
> For example:
> (p:PhilDawes, foaf:knows, ?person) 
> easy to resolve - just dereference p:PhilDawes and you probably
> have the information you need. (I'm using dereference to mean 'look up
> a description').

Well, I'm reluctant to ascribe any status to the information thus found
that requires its use, and I certainly do not agree that it has to be the
information you need.

> However
> (?person, foaf:knows, p:PhilDawes)
> .is much more tricky, since these assertions are likely to be made by
> users external to the domain owner of p:PhilDawes.

Hmm.  I'm not sure of this.  For symmetric properties, it may be somewhat
more likely for a document to put ``local'' URI references in the subject
position, but what about properties that are conventionally written on way
around.  For example, I am more likely to write on one of my web pages

	sps:Sandy ex:loves pfps:Peter .

than I am to write

	pfps:Peter ex:isLovedBy sps:Sandy .

> Here's a straw-man solution:
> - In addition to its bounded description, dereferencing p:PhilDawes
> also provides all the references it knows about.
> - When people author statements refering to p:PhilDawes, they POST
> their triples to the description of p:PhilDawes. (Or maybe a third
> party does).
> - The representation of p:PhilDawes polls the reference URIs it knows
> about periodically to keep its data up to date. (facilitating the
> removal of triples as well as addition)

Independently of the authoritative status of the accessed web page I view
this as extraordinarily dangerous.  There is no way that I would ever
subscribe to a scheme that requires any server that I have control over to
make responses that include

	n666:antichrist owl:sameAs pfps:Peter .

just because some other organization has this triple in some RDF document.
I don't see how any responsible organization would ever subscribe to this
scheme, even if they could somehow tag these ``contributed'' triples as
having come from some other document.


> I am keen to hear any ideas that others may have on the subject since
> in addition to helping bootstrap the semantic web, this is a facility
> that would be very beneficial in my work intranet environment.

I view this as a non-starter, even in a work intranet environment.  Just as
for the Semantic Web as a whole, there is no expectation that such local
environments will have a common view of the world.

> Cheers,
> Phil

Peter F. Patel-Schneider
Bell Labs Research

Received on Monday, 19 April 2004 16:19:57 UTC