10. Extensibility and openness

The preceding pages describe just a few of the concepts contained in the UML metamodel, and the article focuses on introducing the fundamental notions of the language by presenting the graphical formalism on which it is based and illustrating it with a few simple examples of the different types of diagrams available. Our intention here is not to transcribe the entire standard published to date, which is far too rich to be summarized in a few dozen pages. UML unifies and encompasses various modeling techniques that have proved their worth in the IT field, and which enable most software development artifacts to be represented clearly and accurately. However, despite the language's power, UML's expressive capacity remains limited, and the notation is not always suited to the precise, unambiguous formalization of particular phenomena. UML's designers have therefore provided mechanisms for extending...