Software Engineering Institute

The design specification method described in this report treats a software architecture as a set of run-time entities, including tasks and external input/output elements, which interact either via messages or shared data structures. Tasks have a single thread of execution and represent program units that may be executed concurrently. External input elements produce input requests which in turn trigger a set of low level activities to be executed by tasks. External output elements consume results which are produced by tasks. The specification method discussed here facilitates the description of the dynamic structure of run-time entities, the synchronization and communication between these entities, and their resource consumption and production properties (which include timing and sizing).