This section of the documentation describes the current support for inference available within Jena. Note that this is a preliminary version of this document, some errors or inconsistencies are possible, feedback to the mailing lists is welcomed. The Jena inference subsystem is designed to allow a range of inference engines or reasoners to be plugged into Jena.
Such engines are used to derive additional RDF assertions which are entailed from some base RDF together with any optional ontology information and the axioms and rules associated with the reasoner. The primary use of this mechanism is to support the use of languages such as RDFS and OWL which allow additional facts to be inferred from instance data and class descriptions.
However, the machinery is designed to be quite general and, in particular, it includes a generic rule engine that can be used for many RDF processing or transformation tasks.
We will try to use the term inference to refer to the abstract process of deriving additional information and the term reasoner to refer to a specific code object that performs this task. Such usage is arbitrary and if we slip into using equivalent terms like reasoning and inference engine , please forgive us. Applications normally access the inference machinery by using the ModelFactory to associate a data set with some reasoner to create a new Model. Queries to the created model will return not only those statements that were present in the original data but also additional statements than can be derived from the data using the rules or other inference mechanisms implemented by the reasoner.
As illustrated the inference machinery is actually implemented at the level of the Graph SPI, so that any of the different Model interfaces can be constructed around an inference Graph.
