- From: Bijan Parsia <bparsia@cs.man.ac.uk>
- Date: Sat, 5 Jan 2008 22:29:11 +0000
- To: Garret Wilson <garret@globalmentor.com>
- Cc: SW-forum Web <semantic-web@w3.org>
On Jan 5, 2008, at 3:16 PM, Garret Wilson wrote: > Garret Wilson wrote: >> How does RDF justify repeated properties? > > Sorry, maybe I would have been clearer if I would have said, > "multivalued properties", in which a property appears multiple > times for the same resource but with different values, e.g. > > <rdf:Description> > <dc:subject>semantic web</dc:subject> > <dc:subject>database</dc:subject> > </rdf:Description> > > This is an area of conflict with the relational model, and I'm > wondering how RDF justifies this. It's not a conflict. consider the following table version (let's give the blank node an indentifier, ex:foo; blank nodes *are* a departure, but one well handled by "naive" tables or "codd" tables as they are known in the literature). First row are the column headers: ID dc:subject ex:foo semantic web ex:foo database This a perfectly fine relational table (to be a bit loose in terminology). What wouldn't be is: ID dc:subject ex:foo semantic web ex:foo semantic web ex:foo database Since this is a bag not a set. In SQL systems, you do have to deal with the fact of bags (hence the keyword DISTINCT). So, short answer: This isn't a *duplicate* row. It's two rows. Cheers, Bijan.
Received on Saturday, 5 January 2008 22:29:25 UTC