Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.
Jena is open source and grown out of work with the HP Labs Semantic Web Programme.
The Jena Framework includes:
A RDF API
Reading and writing RDF in RDF/XML, N3 and N-Triples
An OWL API
In-memory and persistent storage
SPARQL query engine