returns a new example object based on ALL (train and test) examples in the old set
picks a fixed number of examples, puts them into training sets, rest to test set
SPARQL endpoint knowledge source (without fragment extraction),
in particular for those algorithms which work directly on an endpoint
without requiring an OWL reasoner.
Can assemble sparql queries. can make queries for subject, predicate, object
according to the filter settings object SparqlQueryType, which gives the
predicate and object lists