Diploma Thesis Roles and Collaborations in Scala submitted by

The interrelations of a set of software objects are usually manifold and complex. Common object-oriented program-ming languages provide constructs for structuring objects according to shared properties and behavior, but fail to pro-vide abstraction mechanisms for the interactions of objects. Roles seem to be a promising approach to solve this prob-lem as they focus on the behavior of an object in a certain context. Combining multiple roles yields collaborations, an interesting abstraction and reuse unit. However, existing ap-proaches towards roles in programming languages require vast extensions of the underlying language or even propose new languages. We propose a programming technique that enables role-based programming with commonly available language con-structs. Thus, programmers can express roles and collab-orations by simply using a library, and hence, without the need to change the language, its compiler, and its tools. We explain our proposal on a language-independent level. More-over, we provide an implementation in form of a library for the Scala programming language. Finally, we apply our ideas to design patterns and analyze to which extent these can be expressed and reused with roles.