Specification and analysis of the requirements for embedded software with an external interaction model

This work suggests an early requirements model for embedded software development. It incorporates a system viewpoint to software specification that includes a model of the system external to the software sub-system. Related techniques for specification and analysis of the requirements for embedded software are discussed, as new techniques are sought that build on the old.;The external interaction model developed here employs Statecharts to describe state information of all components. It includes input and output exchange declarations, rules and mappings for these exchanges, and a modeling process.;Two techniques for safety analysis using the external interaction model are given. In the first, a backwards reachability algorithm is used to determine the worst case reachability of unsafe states in the model. The second provides templates for fault tree construction directly from the model. Future research directions are indicated.