jcel: A Modular Rule-based Reasoner

jcel is a reasoner for the description logic EL that uses a rule-based completion algorithm. These algorithms are used to get subsumptions in the lightweight description logic EL and its extensions. One of these extensions is EL, a description logic with restricted expressivity, but used in formal representation of biomedical ontologies. These ontologies can be encoded using the Web Ontology Language (OWL), and through the OWL API, edited using the popular ontology editor Protégé. jcel implements a subset of the OWL 2 EL profile, and can be used as a Java library or as a Protégé plug-in. This system description presents the architecture and main features of jcel, and reports some of the challenges and limitations faced in its development.