Steve Harris wrote:
On 21 Aug 2008, at 16:51, Axel Polleres wrote:
Tackling the question from the more theoretical side,
I like non-monotonic SPARQL queries like the ones modeling set
difference.
E.g.
"Give me all persons *without* an email address" in a certain FOAF graph.
i) It is already folklore, that you can do that with using the
!bound() filter outside an optional, i.e.
SELECT ?X
FROM G
WHERE { ?X a foaf:Person
OPTIONAL { ?X foaf:mbox ?M}
FILTER (! bound(?X) ) }
Shouldn't that be !bound(?M) ?
yup, sorry, typo ... The really nasty trick was anyway the second one
as Lee already remarked ;-)
- Steve
--
Dr. Axel Polleres, Digital Enterprise Research Institute (DERI)
email: [EMAIL PROTECTED] url: http://www.polleres.net/
Everything is possible:
rdfs:subClassOf rdfs:subPropertyOf rdfs:Resource.
rdfs:subClassOf rdfs:subPropertyOf rdfs:subPropertyOf.
rdf:type rdfs:subPropertyOf rdfs:subClassOf.
rdfs:subClassOf rdf:type owl:SymmetricProperty.
