The Systems Biology Ontology is a set of controlled, relational vocabularies of terms commonly used in Systems Biology, and in particular in computational modelling. It consists of seven orthogonal vocabularies defining: reaction participants roles (e.g. „substrate“), quantitative parameters (e.g. „Michaelis constant“), classification of mathematical expressions describing the system (e.g. „mass action rate law“), modelling framework used (e.g. „logical framework“), the nature of the entity (e.g. „macromolecule“), the type of interaction (e.g. „process“), as well as a branch to define the different types of metadata that may be present within a model.