Re: Inferencing on graph patterns

On 14 Nov 2009, at 11:41, Simon Reinhardt wrote:

>> Note, however, that you may get what you want with a different query.
>> For  example, in this case, the
>> SELECT ?type WHERE { ex:C1 rdfs:subclass ?type. }
>> will return all possible types.
>
> Ok. Querying for inferred types was just an example, the initial use  
> case that brought me to this was actually a bit more complex  
> (property restrictions). For this that kind of inferencing would  
> have made the query a lot simpler. But it should still be possible  
> to cover a lot of the inferencing "rules" with SPARQL, especially  
> with property paths. Maybe it's worth investigating at some point  
> how much of OWL 2 RL could be implemented with pure SPARQL - and  
> what extensions would be needed to add the missing bits. But that's  
> just something to keep in mind for the future. :-)

If you fix the entailment regime to RDFS, then very little of OWL2 can  
be encoded in SPARQL, since it is has been shown that the  
computational complexities diverge too much. There are also simple  
counter-examples showing that it does not make sense to have an OWL2  
entailment regime in SPARQL, since you would get unsound results (wrt  
OWL2 semantics) very easily. So, really, SPARQL can hardly go beyond  
RDFS.

cheers
--e.

[1] Enrico Franconi. The logic of RDF and SPARQL: a tutorial. Invited  
talk at the 25th ACM Symposium on Principles of Database Systems  
(PODS-2006), in Chicago IL, on 26-28 June 2006. <http://www.inf.unibz.it/~franconi/papers/franconi-slides-pods-2006.pdf 
 >