- From: Steven Pemberton <steven.pemberton@cwi.nl>
- Date: Fri, 03 Oct 2008 15:47:02 +0200
- To: "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, "Dan Brickley" <danbri@danbri.org>, RDFa <public-rdf-in-xhtml-tf@w3.org>, "www-tag@w3.org WG" <www-tag@w3.org>
- Cc: "Ed Summers" <ehs@pobox.com>
On Tue, 30 Sep 2008 18:16:34 +0200, Williams, Stuart (HP Labs, Bristol) <skw@hp.com> wrote: > Only parially. *iff* the primary topic node were not blank, but a > definite URI node, then merging would world provided that equivalent > nodes were involved. > > However, the identity of blank nodes is scoped only to the graph that > they are in. If you have the two graphs: > > { > _:StevenPemberton foaf:isPrimaryTopicOf <http://www.cwi.nl/~steven/> . > } > > { > _:StevenPemberton foaf:isPrimaryTopicOf > <http://www.w3.org/People/all#steven> . > } > > You cannot determine that they both named resources have the same > primary topic - so the blank topic node in this case is basically > useless establishing that what we have are different accounts of Steven > Pemberton. > > IIUC isPrimaryTopicOf is intended to establish the use of say > http://www.cwi.nl/~steven/ as a subject indicator for Steven Pemberton. > As a subject indicator the resource can only be a subject indicator for > one thing (hence inverse functional) - though there may be many subject > indicators for a given thing. So if we have the merged graph: > > { > ex1:StevenPemberton foaf:isPrimaryTopicOf > <http://www.cwi.nl/~steven/>, <http://www.w3.org/People/all#steven> . > ex2:StevenPemberton foaf:isPrimaryTopicOf > <http://www.w3.org/People/all#steven> . > } > > We can deduce that ex2:StevenPemberton is owl:sameIndividualAs > ex1:StevenPemberton (might be owl:sameAs) from the inverse functional > nature of isPrimaryTopicOf. I'm inclined to say "Well, of course", and I have to admit I still don't see the problem. There are things in the world without URIs (or with URIs that I don't know). I see the use of blanknodes in this way as an existential quantifier "There is a thing that...". Then of course if I say "there is a thing that is the principle topic of A" and "there is a thing that is the principle topic of B" they are not the same thing until I prove they are. But if I say, in two different graphs "there is a thing that is the principle topic of A", then those two things are clearly the same, and so everything I say about that thing in the two graphs can be merged. It all depends how you ground your blank nodes really. Best wishes, Steven
Received on Friday, 3 October 2008 13:51:36 UTC