Use case maps for attributing behaviour to system architecture

The ability to attribute behaviour to architecture is important for the high-level understanding, design, evolution and reengineering of all kinds of systems (from object-oriented programs to parallel and distributed computer systems). Scenarios are a good way of doing it, but popular scenario techniques, such as message sequence charts, that use intercomponent "wiring" as their starting point do not scale up well. Use case maps provide a new, scenario-based way of attributing behaviour to architecture that solves the scale-up problem. The notation enables compact, composite maps to be drawn to represent behaviour patterns of whole systems in terms of causal paths, without reference to "wiring". Through an example, the paper aims to convince software and system engineers that the approach has depth and adds value, despite (and because of) its simplicity and deferment of detail.