An Observer-Based Technique with Trace Links for Requirements Validation in Embedded Real-Time Systems

Sammanfattning: With the growing complexity of embedded real-time systems, requirements validation becomes an ever-more critical activity for developing such systems. Studies have revealed that most of the anomalies, discovered in the development of complex systems, belong to requirement and specification phases. To ease the situation, many efforts have been investigated into the area. Model-based techniques, enabling formal semantics and requirements traceability, are emerging as promising solutions to cost-effective requirements validation. In these techniques, the functional behaviors derived from lower-level requirements are specified in terms of analyzable models at a certain level of abstraction. Further, upper-level requirements are formalized into verifiable queries and/or formulas. Meanwhile, trace links between requirements at various levels of abstraction as well as between requirements and subsequent artifacts (such as verifiable queries and/or formulas, and analyzable models) are built, through which the queries and/or formulas can be fed into the corresponding models. However, such model-based techniques suffer from some limitations, such as how to support semi- or fully-automatic trace links creation between diverse development artifacts, how to ease the demand of heavy mathematics background knowledge to specify queries and/or formulas, and how to analyze models without encountering the state explosion problem.  In this thesis, we cover two aspects centering around requirements validation to ease the aforementioned limitations, which are mainly about requirements traceability and model-based requirements validation. In particular, the technical contributions are four-fold: 1) we have introduced an improved VSM-based requirements traceability creation/recovery approach using a novel context analysis and, 2) we have proposed a lightweight model-based approach to requirements validation by using the Timed Abstract State Machine (TASM) language with newly defined Observer and Event constructs and, 3) we have combined our model-based approach with a restricted use case modeling approach for feature-oriented requirements validation and, 4) we have improved the Observer construct of TASM via proposing a new observer specification logic to facilitate the observer specification, as well as defining the corresponding observer execution process. Finally, we have demonstrated the applicability of our contributions in real world usage through various applications.