3.1. UML-F as a profile
The UML standard provides a number of concepts to extend the language. So-called stereotypes and tagged values are a kind of UML hook concept and form the principal means of specializing or extending the meaning of particular UML elements. Section 3.2 provides a unified enhancement of these two techniques, the enhancement being used to define the UML-F profile.
UML offers another concept for extensions, namely constraints. If used in their full capacity, constraints have a complexity of their own and are not directly useful to our approach. In order to keep UML-F simple, we do not base it on constraints. However, a few simple constraints of standard UML are introduced as tags in UML-F.