- From: Pat Hayes <phayes@ihmc.us>
- Date: Mon, 11 Apr 2011 12:01:06 -0500
- To: Sandro Hawke <sandro@w3.org>
- Cc: RDF Working Group WG <public-rdf-wg@w3.org>
More... On Apr 10, 2011, at 11:50 PM, Sandro Hawke wrote: > 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 ] But that would be a terrible way to express it. Ask yourself: what is this 'thing' whose existence is being asserted and is the subject of these triples? It really is not a *relation*, ternary or otherwise. I mean, the *relation* itself would exist (or, if you are of a nominalist persuasion, not exist) independently of the mere facts of some movie being shown somewhere. Maybe you could say that it is an *instance* of a ternary relation, but even that is an odd way to express oneself. What it is, surely, is a fact or event or circumstance (or situation or occurrent or... ) *in the actual world*, the showing of this movie at this time in this theatre. It has a time and a place, it uses energy and might have legal consequences, this thing. It is **real**. And it – this movie-showing-event-thingie – has a bunch of properties, which these handily binary relations can express in RDF. The point being, that this is a substantive factual assertion about real things in the actual world; it is not a Platonic abstract assertion about things like relations or RDF triples or other syntactic objects. Pat > > 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 > > ------------------------------------------------------------ IHMC (850)434 8903 or (650)494 3973 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
Received on Monday, 11 April 2011 17:01:35 UTC