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Re: Transitive properties (and accessingCollections, and rule WG)

From: Dan Connolly <connolly@w3.org>
Date: Wed, 09 Nov 2005 09:39:50 -0600
To: andy.seaborne@hp.com
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-Id: <1131550791.12579.21.camel@dirk>

On Tue, 2005-11-08 at 13:51 +0000, Seaborne, Andy wrote:
> > http://lists.w3.org/Archives/Public/public-swbp-wg/2005Nov/0036
> Some thoughts:
> David notes that support for transitive closure is an alternative approach for 
> told bNodes.  Support for transitive closure isn't necessary if it is declared 
> outside the query but I think the community expectation will be syntax in the 
> query itself.
> I tried generalizing this to property regular expressions (PRE's) with * + ? 
> () {N,M} operators plus / for path traversal and | for alternative choicies.
> (Not proposing it for this WG.)

Interesting... I think this a design choice relevant to our
postponed accessingCollections issue.

I started composing an [OK?] message to this comment...

Traversing trees with sparql? 
      * 2005-10-26T14:53:28Z from david.h.jones

based on Jos's work...

Updated summary of cwm/euler implementation experience w.r.t. accessing
RDF collections and traversing trees

I was going to say, basically,

  We postponed the issue, because you can do it with SPARQL
  supplemented by rules, as Jos's work demonstrates. OK?

But then I realized the connection between this comment on trees,
Nokia's comments on transitive closure, Wood's comment 2005Nov/0036 ,
and this path expression design noodling.

Meanwhile, W3C just chartered a rule interchange format WG.

So I updated the issues list entry for accessingCollections.
I'll take advice for a little while on whether to
  (a) re-open the issue, and hear arguments that SPARQL
   really needs this sort of path expression in v1 vs
  (b) keep the issue closed and ask the commentor if they're
   satisfied with our rationale.

Support for collections/containers? or trees? or path regular

      * accepted in 2004-09-16 discussion of content selection based on
        client profile in Bristol
      * Note that accessing collections can be done by combining SPARQL
        with inference rules, which, by charter, is orthogonal: 
                The protocol will allow access to a notional RDF graph.
                This may in practice be the virtual graph which would
                follow from some form of inference from a stored graph.
                section 2.1 Specification of RDF Schema/OWL semantics of
                the charter 
      * postponed 22 Feb: 
                RESOLVED: to postpone accessingCollections because 
                      * our not standardizing it doesn't stop anybody
                        from playing
                      * none of the extant designs seems sufficiently
                Clark/UMD, Fukushige/MEI, and 2 others abstaining
      * see also comments Traversing trees with sparql?, Barstow/Nokia,
        esp point 2 on transitive closure
      * WG discussion on using inference rules to supplement SPARQL: Re:
        summary of some cwm/euler implementation experience w.r.t.
        accessing RDF collections 8 Nov 2005
      * WG discussion considering extending SPARQL with graph regular
        expressions: Transitive properties 08 Nov 2005
      * note W3C Launches Rule Interchange Format Working Group

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Wednesday, 9 November 2005 15:39:54 UTC

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