On 3 Mar 2006, at 14:02, Peter F. Patel-Schneider wrote: > For the record, the issue shows up when querying an RDF store that > has been > given > ex:a ex:p ex:c . > ex:a ex:p _:c . > The behaviour of SPARQL depends on the behaviour of the RDF store. > The RDF > store might end up leaning its input, and thus only store > ex:a ex:p ex:c . > or it might maintain the input "as is". My view is that both > stores are > "correct", and that querying should not be able to distinguish > between the two > behaviours. > > However, the SPARQL basic query > ex:a ex:p ?c . > would (most likely) have one match in the leaning case, but two > matches in > the non-leaning case. Peter, you are right with this example. However, please note that the problem of answering in this richer way is np-hard - since you can easily encode the problem of computing lean graphs into this reacher query answering problem. And I guess it is fine not to impose hard computational constraints in this phase. > (This also depends on just how the scoping graph is determined.) Mmhh, I'd say that it does not depend on that: the answer is uniquely determined up to bnode renaming. Why are you saying that? cheers --e.
Received on Monday, 6 March 2006 21:53:44 UTC