A Formal Framework for Modeling External Behavior of an Embedded System As a Black Box Structure

Embedded systems must be high quality systems and the development of embedded systems involves modeling both the external and internal behaviors of the systems. Cleanroom software engineering (CRSE) life cycle methodology concentrates on the quality issues by considering different formal verification and validation methods introduced at different stages of development. CRSE uses box structures that employ formal methods to achieve high quality software systems in specific. In CRSE, the external behavioral modeling is achieved through design of black box structures. CRSE can be used for the development of embedded systems as CRSE methodology is also based on both external and internal behavior modeling. Many methods were proposed in the literature for designing the black box structures that are based on intuition or experience of the designers. Therefore CRSE suffers from lack of formal frameworks to derive Box structures meant for modeling the external behavior. In this paper, a formal architectural framework related to external behavior modeling based on end-to-end processing of the embedded systems represented by thin threads and composite threads is presented that helps in representing the stimulus-response requirements of the embedded systems to be built as Black box structures. The external behavioral model of a pilot project (temperature monitoring and controlling of nuclear reactor system) is presented using the formal framework proposed in this paper.