Jena I

Jena I refers to the initial release and broader family of technologies from the Apache Jena semantic web framework. This framework is used for building semantic web and linked data applications. Key aspects of Jena I, and subsequent versions of Jena, include:

• RDF API: A core component providing an API for creating, manipulating, and querying Resource Description Framework (RDF) graphs. RDF is a standard model for data interchange on the Web.
• Inference Support: Jena provides reasoners that can deduce implicit facts based on explicit RDF data and ontological rules. These reasoners extend the knowledge base beyond what is explicitly stated.
• SPARQL Query Engine: Jena includes a SPARQL Protocol and RDF Query Language engine for querying RDF data. SPARQL is the standard query language for RDF.
• Ontology API: An API for working with ontologies, typically defined in languages like OWL (Web Ontology Language). The ontology API allows developers to programmatically access and reason with ontologies.
• Persistence: Jena supports storing RDF data in various persistence mechanisms, including in-memory models, relational databases (using persistent storage adapters), and native triple stores.
• Rule-Based Reasoning: Jena includes a rule engine that allows for custom inference rules to be defined and applied to RDF data. This enables flexible reasoning beyond standard ontological inference.
• Vocabulary Support: Jena provides predefined vocabulary classes and properties for common semantic web vocabularies like RDF, RDFS, OWL, and Dublin Core. This eases the process of working with these vocabularies.

The term "Jena I" is less commonly used now as the framework has evolved through numerous versions, typically just being referenced as "Apache Jena". However, when discussing the foundational principles and technologies from the beginning of the project, "Jena I" can implicitly be understood.