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Re: reification test case

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 06 Feb 2002 15:10:35 -0500
To: seth@robustai.net
Cc: www-rdf-logic@w3.org
Message-Id: <20020206151035Q.pfps@research.bell-labs.com>
From: "Seth Russell" <seth@robustai.net>
Subject: Re: reification test case
Date: Wed, 6 Feb 2002 11:44:23 -0800

> From: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
> 
> > > > > <rdf:description>
> > > > > <rdf:type>:Statement</rdf:type>
> > > > > <rdf:subject>:Gore</rdf:subject>
> > > > > <rdf:predicate>:wonThe</rdf:predicate>
> > > > > <log:truthValue>False</log:truthValue>
> > > > > </rdf:description>
> > > > >
> > > > > which holds for all such statings.
> > > > >
> > > > > But I could also write:
> > > > >
> > > > > <rdf:description>
> > > > > <rdf:type>:Statement</rdf:type>
> > > > > <rdf:subject>:Gore</rdf:subject>
> > > > > <rdf:predicate>:wonThe</rdf:predicate>
> > > > > <dc:author>:Seth</dc:author>
> > > > > <log:truthValue>False</log:truthValue>
> > > > > </rdf:description>
> > > > >
> > > > > which holds for a smaller collection of statings.
> > > >
> > No, but I certainly didn't see anything to indicate that the first is
> about
> > a statement and the second about a stating.
> 
> The first refers to all statings with those three properties which are
> False.   The second refers to a subset of those which were authored by me
> which are False. In other words a reification node with not other
> qualifications is as close to refering to the ideal triple as we need to
> come.

HUH?  How can this be?  The resources above are *resources*, i.e., single
elements of the domain.  There is nothing that I can find anywhere in RDF
or RDFS that indicates that any particular resource aside from collections
refers to a set of anything.

How can the first resource above refer in RDF (or RDFS) to ``all statings
with those three properties which are False''?  There is something that I
do *not* understand in your claim above.  Please indicate how you have come
by this understanding of RDF(S).

[...]

> > > Do the following two nodes refer to the same thing or "have equivalent
> > > status as far as RDF is concerned" ?
> > >
> > > [a :Book; title "Knowledge Representation"; dc:author "John F. Sowa"]
> > > [a :Book; title "Knowledge Representation"; dc:author "John F. Sowa";
> > > :ownedBy "Seth Russell" ; :sittingOn :MyDesk]
> >
> > They don't necessarily refer to the same thing, but they certainly have
> the
> > same status.
> 
> Well, I have no idea what you mean by 'status'.
> 
> >RDF knows nothing about :ownedBy or :sittingOn that causes
> > the first resource to have to refer to a book (as in a title) and the
> > second to have to refer to a book (as in a physical collection of paper
> > sheets bound together).  Do you think that it has?
> 
> No.  RDF doesn't know anything about anything except  'rdf:type' and the
> properties we are arguing about.  Obviously we have to publish a schema to
> give meaning to our terms.  I don't see your point.

The point is that you seem to be aiming toward the view that there is some
difference in essence between the RDF meanings of the two resources just
above.  The two things above are just resources, nothing more, nothing
less.  They are the subject of several RDF statements (three for the first
and five for the second), one of which is given a slight bit of extra
meaning by RDFS, but nothing to indicate that there is a type/token
distinction between them.

> >Do you think that this
> > situation is any different from the situation with the two resources
> > earlier in this message?
> 
> No .. and that was my point.

And my point also.  The two resources at the beginning of this message are
resources.  They do have a slight bit of extra meaning by virtue of their
status as the subject of statements with pred rdf:type and obj
rdf:Statement, but this is a very slight bit of extra meaning.  Certainly
there is no way that RDF or RDFS is saying anything very deep about them,
particularly about any relationship between each of them and a *set* of
statings.  Any such connection is completely outside of RDF and RDFS.

> Seth Russell

It appears to me that for years now people have been reading *much* more
into RDF and RDFS than is really there.  RDF and RDFS are semantically
nothing more than what is captured by the new model theory (plus two simple
additions to deal with reification and collections, but both of these
additions are extremely weak).

[Well, actually there are a few things in RDF and RDFS that are not in the
model theory, including
1/ the prescriptive reading of domain and range (removed by the RDF Core WG)
2/ the non-circularity of subclass and subproperty (removed by the RDF Core WG)
3/ alternative collections (probably removed by the RDF Core WG)
4/ some syntax stuff, like abouteachprefix (partly removed by the RDF Core WG).]


Peter F. Patel-Schneider
Received on Wednesday, 6 February 2002 15:11:28 GMT

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