Core meta-modelling semantics of UML: The pUML approach

The current UML semantics documentation has made a significant step towards providing a precise description of the UML. However, at present the semantic model it proposes only provides a description of the language's syntax and well-formedness rules. The meaning of the language, which is mainly described in English, is too informal and unstructured to provide a foundation for developing formal analysis and development techniques. Another problem is the scope of the model, which is both complex and large. This paper describes work currently being undertaken by the precise UML group (pUML), an international group of researchers and practitioners, to address these problems. A formalisation strategy is presented which concentrates on giving a precise denotational semantics to core elements of UML. This is illustrated through the development of precise definitions of two important concepts: generalization and packages. Finally, a viewpoint architecture is proposed as a means of providing improved separation of concerns in the semantics definition.