With origins in antiquity and ancient philosophers speculating on the nature of being, ?ontology? and ?ontological modelling? have perhaps a reputation of being esoteric, impenetrable and only for the purist of academics.In the last couple of decades however, there has been great work done to make ontological concepts and models readily accessible and to build the essential toolkits required to apply them at a practical level.The Ontology Working Group (OWG) provides an introduction to ontology, explains how relevant and important it is and describes the OWG's current objectives in developing new ontological models that will be of benefit to everyone working in domains that involve the management of risk, such as safety and security.