KR'12 Presentation of two techniques for efficient reasoning and query answering in DL-Lite (OWL 2 QL). First, Semantic Index, a technique to store triples (ABoxes) in a way that already encodes all the entailments of the ontology (RDFS or OWL 2 QL) in the backend, allowing for reasoning without exponential rewritings or forward chaining. The technique can easily be used to construct very efficient triple stores with inference support. Second, a TBox optimisation technique that allows to obtain simpler TBoxes when the triples (ABoxes) satisfy a set of constraints.