Ontologies are a popular research direction in different domains as is also the case in information systems research. In the beginning of this millennium Geerts and McCarthy (2002) proposed an ontology for the business context which was an extension of the basic REA-model which had already proven its use as a semantic accounting information model. In the recent papers of Geerts and McCarthy the focus is primarily on defining and theoretically justifying the content of this newly proposed enterprise ontology. In this paper we elaborate on more practical issues related to the REA-ontology. A lot of confusion exists about what ontologies are and for what purpose they can be used. In this paper we investigate how we could classify the REA-ontology and the REA-ontology applications. This analysis clarifies the application potential of the REA-ontology but also emphasizes that a generally accepted, explicit and formal specification is needed in order to improve the usability. In the case of the REA-ontology this means that the ontology should be more unambiguously to interpret by business experts and the applicability for ontology-driven system development and ontology driven systems should be improved. This paper proposes a new REA-ontology specification that uses an UML profile for graphically representing ontologies (OMG 2006). This specification of the ontology in a single graphical representation formalism is more complete than previously available representations, without compromising its ability to be understood by business professionals. At the same time it can easily be transformed into a more formal representation which can be understood by machines. Having a machine readable representation of the REA-ontology is a necessary prerequisite for the successful application of the REA-ontology in business modeling, software engineering, knowledge representation and interoperability creation.
