On Types, Instances, and Classes in UML

The semantics of UML [3] is for a large part given in English. The drawback of Eng-lish is its ambiguity, which makes it unclear and ambiguous. But the benefits of Eng-lish are its power and flexibility, which allow it to deal with a slightly inconsistent terminology. Formalizing UML will imply recognizing the occurrences of these in-consistencies and coping with them in a systematic way. In this paper, we show some problems with the UML terminology and we propose an approach to deal with these problems.