Apache Jena is an open-source Java framework for building semantic web and linked data applications. It provides a set of libraries and tools for managing RDF (Resource Description Framework) data, performing SPARQL (SPARQL Protocol and RDF Query Language) queries, and building applications that process and reason over semantic data.

Some key features of Apache Jena include:

1. RDF data model: Apache Jena allows you to represent and manipulate RDF data, a standard graph-based model for representing structured information. It provides classes and APIs for creating, reading, writing, and modifying RDF graphs.

2. SPARQL query engine: Jena includes a powerful SPARQL query engine that allows you to query RDF data using the SPARQL query language. It supports all features of SPARQL 1.1 and provides advanced query optimizations for efficient query processing.

3. RDF storage: Jena provides different storage options for RDF data, including in-memory models, persistent triple stores, and distributed storage systems. It supports popular RDF storage technologies such as Apache TDB and Apache Jena Fuseki.

4. Reasoning capabilities: Apache Jena includes a rule-based reasoner that allows you to apply inference rules to your RDF data. This enables you to derive new knowledge from existing data and make implicit relationships explicit.

5. RDF serialization formats: Jena supports various RDF serialization formats, including RDF/XML, Turtle, N-Triples, N-Quads, JSON-LD, and RDF/JSON. It provides parsers and writers for converting between these different formats.

6. Integration with other frameworks: Jena can be easily integrated with other Java frameworks and libraries. It provides APIs for reading and writing RDF data from and to various sources, including files, databases, and web services.

Overall, Apache Jena is a comprehensive and flexible framework for building semantic web and linked data applications. It provides powerful tools and libraries for managing and processing RDF data, performing SPARQL queries, and building intelligent applications that leverage the power of semantic technologies.