- From: Jan Grant <Jan.Grant@bristol.ac.uk>
- Date: Thu, 15 Nov 2001 15:28:36 +0000 (GMT)
- To: Dan Connolly <connolly@w3.org>
- cc: Pat Hayes <phayes@ai.uwf.edu>, w3c-rdfcore-wg <w3c-rdfcore-wg@w3.org>
Warning: ramble, vague unease, and potential can of worms. On Thu, 15 Nov 2001, Dan Connolly wrote: > Pat Hayes wrote: > > > the question of whether two blank nodes are the 'same' or 'different' > > is settled in the syntax itself. This, in the graph syntax there are > > no bound variables, or local names, or anything at all with a local > > scope. > > phpht. How are blank nodes not bound variables? Actually, I've been worrying about this recently. We have, in a nutshell, 1. a bNode is an existentially quantified variable and this is something I find slightly disturbing. I'd much rather replace it with: 2. a bNode (anonymous resource, whatever - leaving aside the "is it a literal?" question for the moment) is a node that we don't know the label of Why? Well, first note, that this (ie, a node with conceptual identity what we just happen to be somewhat ignorant of) entails the same thing as the current MT - ie, it's making an existentially-quantified statement. Now look at some common questions that I've asked, others have asked, and even Pat asked at the F2F... "how do I assert additional information about that node?" "how do I find that node again?" etc. etc. These questions are, from a MT point of view, missing the point. But I've had discussions with DB implementors for whom the common intuition follows the "thing we don't know the name of" line rather than the "existential variable" one. The MT obviously doesn't deal with process issues - how do we assert, pass around, delete, transform bits of an RDF graph in an implementation. That's not its job. The MT doesn't actually change much (at all?) if you take the second point of view above. What does change is the reasonable expectation of supported (supportable) operations on an RDF store. Can we get away with this? [ I guess I owe Sergei an apology - however, I'm still not suggesting we invent UUIDs for anonymous nodes, just reconsider what they mean. ] jan PS. Pat, please shoot me down. -- jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/ Tel +44(0)117 9287088 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk Axioms speak louder than words.
Received on Thursday, 15 November 2001 10:31:05 UTC