Multifunctional software systems: Structured modeling and specification of functional requirements

This paper deals with the structured specification of interface behavior of multifunctional systems, which are systems that offer a variety of functions for different purposes and use cases. It introduces a theory and first concepts of a methodology for the identification, structured modeling, and formalization of functional requirements of multifunctional systems. Service hierarchies specify multifunctional systems in terms of their provided sub-functions called services together with their mutual relationships and dependencies. A service hierarchy describes the functionality of multifunctional systems in a structured way. Each service is specified independently and the specification is added to the service hierarchy. Modes help to specify the feature interactions and by that functional dependencies between the services. The approach is based on the Focus theory for modeling interface behavior and services.