UTP12 — Alter predefined interfaces to stereotypes with constraints

The UTP predefines three interfaces, that are Scheduler, Arbiter and Timer. Mixing interfaces and stereotypes, which are supposed to work with those interfaces, is confusing and complicates the implementation of the profile. The idea of those interfaces is straight forward, however, the technical realization is hard to achieve due to mixed meta layers. UML::Interfaces instances are located at meta layer M1 (model layer), whereas Stereotype instances are located at meta layer M2 (meta-model layer).

Since the profile mechanism allows the definition of constraints for the base class of a stereotype, it is possible to express the semantics of the predefined interfaces with stereotypes and constraints, being applied on them. Even if a UML profile tool does not include OCL evaluation, the profile would be still easily implementable. The key point is here: Including OCL constraints into the semantics of a stereotype does not restrict the technical feasibility of the profile. Rather, the modeler would be responsible to respect the constraints of the stereotype. If a tool makes use of OCL expressions, the validity of the model would be checked automatically.