RE: How does RDF/OWL formalism relate to meanings?

> From: Bijan Parsia [mailto:bparsia@isr.umd.edu]
> Sent: Sunday, April 11, 2004 11:23 PM
> 
> On Apr 11, 2004, at 11:04 PM, John Black wrote:
> [snip]
> > In the RDF Semantics Recomendation it states:
> >
> > "1.2 URI references, Resources and Literals.
> > This document does not take any position on the way that 
> URI references
> > may be composed from other expressions, e.g. from relative URIs or
> > QNames; the semantics simply assumes that such lexical 
> issues have been
> > resolved in some way that is globally coherent, so that a single URI
> > reference can be taken to have the same meaning wherever it occurs."
> > - http://www.w3.org/TR/rdf-mt/#urisandlit
> >
> > What is the effect of the language, "...so that a single URI
> > reference can be taken to have the same meaning wherever it 
> occurs."?
> > How important is this assumption to RDF semantics?
> 
> Upon reflection, that isn't the best wording.
> 
> Roughly: In the *graph* there are only absolute URIs. There 
> also are no 
> contexts, so every node labeled with the same uri is equivalent.
> 
> *Between* graphs, however, URIs can behave quite differently 
> (until you 
> merge them).
> 
> I'd say it's pretty important :)

And merging graphs would seem to be a factor affecting my ability 
to say what I mean when using the descriptive naming provided 
by functional and inverse functional properties.

Lets say I create a URI within a descriptive graph using, 
UsGov:SSNo :123456789 and foaf:mBox :mailto:JohnBlack@mysite.com 
as inverse functional names (properties) for my concept of me.  
Then I can use this descriptive graph to signify me in an on-line 
resume, for example, and say that my title is 'Senior Software 
Architect'.  But so can anyone else use those inverse functional 
names in descriptive property graphs to make statements.  Peter 
may feel the need to dispute me and put a graph on his web site 
saying that UsGov:SSNo :123456789 has the foaf:mBox 
:mailto:Peter@hissite.com and has the title 'President of the 
United States'.  When the sw-google global search/inference engine 
merges the two graphs, what happens to my meaning?  Who are my 
statements about?

So how do I communicate to sw-google that when I post an on-line 
resume in RDF, and post a descriptive RDF graph to signify me, so I 
can make RDF statements about me, that it should interpret my graph, 
and not Peter's, to determine who I meant to be the subject of the RDF 
statements of my resume?

It seems to me that if a human interprets the RDF, they might parse 
the mailto:JohnBlack@mysite.com semantically and realize that the 
@mysite.com is the same as the mysite: prefix of the resume 
statements on my site and conclude that statements located on my site 
were more authoritative about who I was referring to than the statements 
made on Peter's site.  But RDF/OWL engines are not required to do this, 
because the RDF semantics ignore the URI semantics.  
"There are several aspects of meaning in RDF which are ignored by 
this semantics; in particular, it treats URI references as simple names, 
ignoring aspects of meaning encoded in particular URI 
forms [RFC 2396]..." - http://www.w3.org/TR/rdf-mt/#intro

These topics were discussed extensively last year.  But while I can see 
the value of the ability to dispute the factual validity of RDF 
statements, using RDF statements, I don't see the same value in the 
ability of someone to dispute who or what I mean to refer to by a name 
or a term or a descriptive graph.

To go back to a previous example, it doesn't seem that useful 
if I were a math teacher and wrote on the board, as the preliminary 
givens of an example, 'let a = 3' and 'let b = 4' and one of my 
students jumped up and said 'No, no, no.  I dispute that a = 3'  On 
the other hand, if I state that 3 = 4, there is an obvious need for 
others to be able to dispute that and say, '3 <> 4'.

> Note that URIs in literals (e.g., in literals of datatype xsd:anyURI) 
> are exempt from this merging. So the above text isn't quite right if 
> you try to read it in full generality.
> 
> Cheers,
> Bijan Parsia.
> 
>

Received on Monday, 12 April 2004 12:39:40 UTC