Abstract: A utility transforms a class diagram representing an ontology, such as a UML class diagram, into a fully-described, standard representation of an ontology such as OWL file. It may be based on Rational Software Architect (RSA) and its model transformation capabilities. The RSA transformation framework uses a Visitor-like pattern for iterating over all of the UML elements in a UML diagram. The framework allows the developer to configure ‘Rule’ classes that are executed when different types of UML elements are encountered. Each UML element is visited once, which causes each rule to be fired for each element type. Rules are configured for just those UML types that are of interest to the transformation, for example classes, primitives, properties, packages and instances. Each rule in the implementation is then written to delegate to a Registrar class, which has a method for building the ontology model from the registered UML elements.