ObdalibQuestIntro
Quest is a SPARQL engine that supports RDFS and OWL 2 QL entailment regimes. Quest can work in two "data modes" that define how the data is given to Quest.
Virtual RDF Graph mode (a.k.a. Virtual ABox mode). In this mode Quest receives as input an RDFS/OWL2QL ontology and a set of mappings (in an .obda file). Quest will use the mappings to translate SPARQL queries over the ontology into SQL queries over the data base defined in the .obda file.
The functionality of this mode is very similar to that offered by system like D2R Server and Virtuoso RDF views. However, the technique used to generate the SQL queries is very efficient, and generates very fast SQL queries, which can give Quest much better performance than other systems.
Classic RDF Graph mode (a.k.a. Classic ABox mode). In this mode Quest works similarly to a traditional OWL reasoner or triple store in the sense that it will take as input an ontology AND data triples/ABox assertions. The interesting aspect of this mode is that Quest uses the same mechanism for query answering than that used in virtual mode. That is, Quest will also use mappings and a database, however, in this case the database (schema and data) and the mappings of the OBDA model are defined and managed by Quest itself. The database used at the moment is an in-memory H2 database.
