CEL—A Short System Demonstration

Description logics (DLs) are an important family of formalisms for reasoning about ontologies. CEL (Classifier for EL) is a free (for non-commercial use) LISP-based reasoner for the description logic EL [2], supporting as its main reasoning task the computation of the subsumption hierarchy induced by EL ontologies. The most distinguishing feature of CEL is that, unlike other modern DL reasoners, it implements a polynomial-time algorithm, which allows it to process very large ontologies in reasonable time. The underlying description logic EL is a practically useful sub-language of EL introduced in [1]. Despite being less expressive than other description logics such as SHIQ and OWL, it offers a selected set of expressive means that are tailored towards the formulation of biological and medical ontologies, some of the most prominent of which are the Gene Ontology (Go) [7], the Galen Medical Knowledge Base (Galen) [5], and the Systematized Nomenclature of Medicine (Snomed) [3, 6].