Re: Proposed change to the OWL-2 Direct Semantics entailment regime

On 30 Nov 2010, at 14:51, Lee Feigenbaum wrote:

> On 11/30/2010 9:49 AM, Enrico Franconi wrote:
>> I repeat myself: *any* OWL-QL or OWL-EL implementation by design incorporates BGPs with OWL Direct Semantics in the manner I'm proposing.

This is pretty obviously false, afaict. But maybe you were being hyperbolic? Nothing prevents an engine with non-distinguished variables + existential variable interpretation of bNodes in data from leaving the query engine untouched and skolemizing the data on input.

To handle bNodes correctly would require a rather more elaborate preprocessing step (but doable).

>> Not having BGPs in the manner I'm proposing would force them not to adopt SPARQL for their systems.
> Thanks, Enrico.
> Birte and Bijan -- if all current SPARQL implementations that incorporate OWL QL or OWL EL semantics behave in this way, wouldn't we be facing a significant implementation cost to keep the spec "as is"?

I believe that even Quanto forbids bnodes in data, so isn't so very relevant.

But no, I don't think the implementation cost is high.

> i.e. wouldn't we be asking all current SPARQL-OWL implementations to change their behavior?

The big one is returning bNodes, as Enrico pointed out. But the gain in SPARQL/RDF compatibility would be worth it, IMHO.


Received on Tuesday, 30 November 2010 15:32:45 UTC