- From: Steve Harris <steve.harris@garlik.com>
- Date: Mon, 2 Oct 2006 10:29:00 +0100
- To: Bijan Parsia <bparsia@cs.man.ac.uk>
- Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
On 2 Oct 2006, at 10:14, Bijan Parsia wrote: > > Sorry to be late, but there was some confusion about what was going > on and then I hit the class part of the week. > > I think the status part should point to the issues list. > > """Costs: Tableau-based reasoners (at least, the Pellet Demo > example 7) rely on the current, more expressive semantics to match > implications that are not in a materializable RDF graph.""" > > No. Pellet uses BNodes as syntax for non-distinguished variables, > as that's what we were told was the likely syntax for non- > distinguished variables in SPARQL/DL. The semantics of *all* > variables in SPARQL/RDF is semi-distinguished. > > I thought the alternative proposal (e.g., from conversation with > Jeen, Jorge and others) was to *drop* BNodes in triple patterns. > That does solve all the problems of scope, meaning etc., but it > means that certain combinations of the axes of distinguishedness > will be harder to specify (but heck, we can always introduce syntax > later). > > """@@ Now we are in CR, shouldn't this be deleted? Need chair's > permission. > The working group decided on this design and closed the disjunction > issue without reaching consensus. The objection was that adding > UNION would complicate implementation and discourage adoption. If > you have input to this aspect of the SPARQL that the working group > has not yet considered, please send a comment to public-rdf-dawg- > comments@w3.org.""" I believe that at the time OPTIONAL did not allow shared variables on OPTIONAL clauses that weren't in the parent clause. It makes a big difference to the complexity of the implementation. - Steve
Received on Monday, 2 October 2006 09:29:15 UTC