Dave Reynolds wrote:
On Wed, 2011-10-05 at 11:22 +0100, Paolo Castagna wrote:
Dave Reynolds wrote:
If you just want to list the properties and classes that are used then
you can do things like:
SELECT DISTINCT ?p WHERE {?s ?p ?o.}
SELECT DISTINCT ?cls WEHRE {?i a ?cls.}
Any idea to speed up these two queries (for large TDB datasets) is welcome! :-)
I nearly put a comment in that response that those can be very expensive
queries :)
:-)
The fact is that often people do not put vocabularies|ontologies in their data
(rightly so). They also want to have a list of properties and classes actually
used in a dataset, and they want counts (i.e. how many times a property or a
class has been actually used in a dataset).
The list of properties (with counts) can be derived from the stats.opt file
(if present).
Maybe people wanting to have super fast list of distinct properties|classes
actually used in a dataset should have a custom index just for that.
However, one would need to intercept all updates operation and keep those
indexes in sync with TDB indexes. I have no idea on what is the best way to
do that.
Are there better ideas?
Paolo
Dave
