Re: Distributed querying on the semantic web

Hi Peter,

From what I can gather, your concerns and objections are based around
issues of trust and authority - neither of which I attempted to
address in the original mail. I am purely attempting to address
the problem of information discovery in the early stages of the SW.

Answers inline:

Peter F. Patel-Schneider writes:
 > 
 > From: "Phil Dawes" <pdawes@users.sourceforge.net>
 > 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.

Yes - sorry if that wasn't clear.

 > 
 > 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 http://www.whitehouse.gov just because I use the URI
 > http://www.whitehouse.gov/#GeorgeWBush, *even* if this information is only
 > something like
 > 	http://www.whitehouse.gov/#GeorgeWBush rdf:type foaf:person .
 > 

If your application is going to use information gleaned dynamically
from the web, then you're going to have to deal with this somehow.


 > > 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) 
 > > 
 > > ..is 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.
 > 

I'm not sure how you got the idea that it *has* to be the information
you need - apologies if I gave that impression. 
I am merely attempting to envisage a simple facility for getting
*some* information about a URI when you have none. 
At present this is impossible without using some previously-known
centralised service.


 > > 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 .
 > 

True. - That is a problem with 'consise bounded descriptions' as
described by the URIQA[1] proposal - this statement wouldn't appear in
the description for pfps:Peter.

 > > 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.
 > 

That's fine. You own the ___domain (or at least the namespace) and so
have complete control over which triples you return in response to a
query. If people don't like what you return, they'll probably use a
different term.

I suspect that for trust to work on any implementation of an
open-world semantic web (centralised or decentralised), the authority
of a statement will have to be decoupled from the ___location it was
discovered. If that is the case, then it won't matter if you serve the
statement or it comes from somewhere else.

 > [...]
 > 
 > > 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.

Actually this already works to a certain extent (and adds value) in my
work intranet environment. We have a facility (in use) that returns
RDF contact information for an employee by dereferencing the HTTP URI
denoting that employee (via a 301-see-other). N.B. This only works
because the applications using the facility trust it.

Without such a facility on the semantic web, I struggle to see how it
will be bootstrapped to deal with open queries. At present, there is
no real 'web' of information to search.

Cheers,

Phil

[1] http://sw.nokia.com/uriqa/URIQA.html

Received on Monday, 19 April 2004 18:04:24 UTC