In order to handle the large amount of variability in product families, automated product derivation support is desirable. To make automated product derivation possible one important ingredient is that the solution domain should be formalized. This should allow the formal description of the variability and the formal description of the choices. Such a formalization should be presented to the application engineer in a way that gives insight in the functioning of the system. To give insight in the structure and functioning of a software system at a high-level of abstraction, an architectural description is often used. Lately, socalled ADL’s (Architectural Description Languages) have been introduced for allowing clear architectural descriptions with well-defined semantics. It is the contribution of this paper to provide an ADL extension called AVDL (Architectural Variability Description Language), which allows formalizing variability at the architectural level. Relevant aspects of AVDL ...