Jena—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.
Joseki—an HTTP engine that supports the SPARQL Protocol and the SPARQL RDF Query language.
ARQ—a query engine for Jena that supports the SPARQL RDF Query language.
TDB—Jena component that provides large scale storage and query of RDF datasets using a pure Java engine and SPARQL.
SDB—Jena component that provides for scalable storage and query w/ SPARQL of RDF datasets using conventional SQL databases for use in standalone applications, J2EE and other application frameworks
Sesame—an open source framework for storage, inferencing and querying of RDF data.
Pellet—OWL 2 reasoner for Oracle Database 11g R2, providing scalable and correct OWL reasoning.
D2RQ—declarative language to describe mappings between relational database schemata and OWL/RDFS ontologies, enables applications to access a RDF-view on a non-RDF database through the Jena and Sesame APIs, as well as over the Web via the SPARQL Protocol and as Linked Data.
Jetty—provides an HTTP server, HTTP client, and javax.servlet container.
Cytoscape—Open source visualization tool for graph data