Introduction to systems engineering with use cases

Systems engineering copes with complexity by organising development hierarchically into subsystems, some being software. Use cases are organised collections of scenarios, used to define the purposes of systems and software. They are well established in software engineering but more controversial for systems. Well organised use case models are suitable for eliciting and analysing functional requirements at all levels in a system. A companion contribution will look at non-functional requirements. Use cases increase clarity and assist with requirement reuse.