A Formal Approach to Specifying the Functionality of Software System Families

Addressing the challenges faced today during the development of multi-functional system families, we suggest a service-oriented approach to formally specifying the functionality and, particularly, the functional variability already in the requirement engineering phase.\\ In this paper, we present and precisely define the underlying concepts, such as the notion of individual services, the combination of services, and variability.\\ Thereby, in contrast to prevalent approaches, we especially focus on explicitly modeling behavioral (functional) commonalities and differences between alternative variants.