W3C home > Mailing lists > Public > www-rdf-logic@w3.org > February 2002

Re: reification test case

From: Seth Russell <seth@robustai.net>
Date: Wed, 6 Feb 2002 09:35:11 -0800
Message-ID: <00ae01c1af34$a0e35de0$657ba8c0@c1457248a.sttls1.wa.home.com>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: <www-rdf-logic@w3.org>
From: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>

> Well one might argue that
>
> 1/ there is at most one statement with a given predicate, subject, and
object

Ok, but can we restate that?  There is at most one *triple* with a given
predicate, subject, object.

> 2/ each triple, i.e., each potential statement, has at most one
reification
>    in the form of a member of rdf:Statement

I believe that rdf:Statement is a class and not a set, so your use of the
word 'member' here is problematic.  Don't forget there is normally no global
identity to a node of rdf:type statement; it is just a Bnode, and as such
there is nothing that is special about the rdf:subject, rdf:predicate, and
rdf:object properties of that Bnode - they do not confer any special kind of
identity to the node, and the current MT does not smush them together.

> Why?  Well precisely so that one can uniquely identify a potential
statement
> and make statements about that statement.

Now I suppose we could put some kind of identity on a reified statement that
could imply that it referred to the one and only triple in the current tidy
graph, or even perhaps to the one and only abstract triple in the sky - but
me thinks we should invent a new property arc for that purpose.   Perhaps
that might be a way for us to have it both of our ways :)

>For example, one could in this
> way relate the statement to log:false via log:truthvalue, or use it in a
> log:implies construct.

I don't see why we can't do that right now.  I could write

<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.

> Well I don't see this as *broken* so I'm not lobbying for any change.  I'm
> not lobbying against the change also.  However, I am arguing that it would
> be a *change*, not a fix or a clarification.  It may be that the RDF Core
> WG will decide on the change.  If so, fine, or at least I would go along
> with the change.  If not, also fine, at least by me.

:))

Seth Russell
Received on Wednesday, 6 February 2002 12:38:53 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:52:41 GMT