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Re: RDF-ISSUE-25 (Deprecate Reification)

From: Sandro Hawke <sandro@w3.org>
Date: Mon, 11 Apr 2011 00:50:43 -0400
To: Pat Hayes <phayes@ihmc.us>
Cc: RDF Working Group WG <public-rdf-wg@w3.org>
Message-ID: <1302497443.2180.24.camel@waldron>
On Sat, 2011-04-09 at 08:49 -0500, Pat Hayes wrote:
> > ] ISSUE-25 is about the RDF reification vocabulary, which is a
> > ] built-in vocabulary for reifying *statements*. You are talking 
> > ] about a common modeling practice in domain vocabularies for
> > ] reifying *relationships*. That has nothing to do with ISSUE-25.
> > 
> > Right, that was what I wanted to have explicitly clear. It's not the
> > idea or practice of reification that is to be deprecated but the
> > baked-in support for reifying binary relations.
> No, really, you have this wrong. It IS the idea of reification that is
> being deprecated; and this device that you have mentioned, of encoding
> an n-ary relation using a bundle of binary 'role' relations, is NOT
> reification. The two things are distinct. Using the name of one to
> refer to the other is going to cause a lot of confusion. Reification
> is using RDF to *describe* other pieces of RDF. 

Pat, I'm a little confused here.   What I think William is saying sounds
right to me, so I don't know why you're calling it wrong.

If we have ternary relationship "showing", between a movie, a show-time,
and a theater, and we want to represent that in RDF, we have (as you've
both pointed out) several options.   If we have a lot of similar ternary
relations, we might choose a  generalized representation like this:

 [ :ternaryRelation movie:showing;
   :op1 "The Sound of Music";
   :op2 "2011-04-11T12:40:00Z"^^xs:datetime;
   :op3 eg:SomeTheater ]

We could of course do something similar for any particular arity
relation.   If we did it for the 2-ary case it would look exactly like
2004 RDF reification, wouldn't it?

Now, William's example [1] was more like:

 [ a movie:Showing;
   movie:title "The Sound of Music";
   movie:showtime "2011-04-11T12:40:00Z"^^xs:datetime;
   movie:theater eg:SomeTheater;

... but the difference between my two examples doesn't seem to me to
cross a bright line, where the first is the evil reification and the
second is recommended practice.  If you see a bright line there, could
you try to make it more clear for me what exactly it forbids?   Thanks.

     -- Sandro

[1] http://lists.w3.org/Archives/Public/public-rdf-wg/2011Apr/0232.html
Received on Monday, 11 April 2011 04:50:51 UTC

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