W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2001

Re: Bags (was: closing semantic issues)

From: Dan Connolly <connolly@w3.org>
Date: Thu, 08 Nov 2001 12:51:17 -0600
Message-ID: <3BEAD425.60108@w3.org>
To: Pat Hayes <phayes@ai.uwf.edu>
CC: Graham Klyne <Graham.Klyne@MIMEsweeper.com>, w3c-rdfcore-wg@w3.org
Pat Hayes wrote:

>> At 05:35 PM 11/6/01 -0600, Pat Hayes wrote:

>> if we then learn that _:b1 and _:b2 are equivalent,
> 
> 
> ....but wait. Do we want to consider reasoning with equivalences at all? 


We certainly don't want to preclude it; the DAML+OIL stuff wouldn't
layer on top, otherwise, would it?

> That gets us into a whole lot of tar-pits which we might want to just 
> try to avoid, maybe (please?)

[...]


> So heres the rule. If we have a triple
> 
> foo rdf:type rdf:Bag
> 
> in a graph, then say that the nodes which are in the object position of 
> a triple of the form
> 
> foo rdf:_n <object>
> 
> in that graph are the 'foo member nodes'.


No; you can't conclude from no information that there are no others.

And I do think that each of the _:n properties is functional;
i.e.
	_:x rdf:_1 "abc".
	_:x rdf:_1 "def".
is a contradiction (is that in the model theory? subject/predicate/object
are also functional).

So the best I can think of is that if we have

  _:b rdf:type rdf:Bag.

then there's some _:bc where

  _:b rdfs:bagContents _:bc.


and where any X with

  _:b rdf:_NNN X.

we have

  X rdf:type _:bc.

(hmm... that might end up with a literal subject. That
doesn't bother me, but if it bothers other folks,
I suppose some analog of ICEXT, say IBAG is in order.
Ug... this the second really serious design bug
I've seen with RDF containers).

> Then any graph gotten by 
> permuting the arcs to the foo member nodes, and replacing  the node foo 
> by a new bnode, should be entailed by the first graph.
> 
> Tell you want, lets agree not to talk about rdf:Bag-closures, OK?


I'm not sure what a bag-closure is, but if it's the same issue as


   http://www.w3.org/2000/03/rdf-tracking/#rdfms-seq-representation

then I don't agree not to talk about it ;-)

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 8 November 2001 13:51:21 EST

This archive was generated by hypermail pre-2.1.9 : Wednesday, 3 September 2003 09:42:34 EDT