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J. Trojer:
"Requirement Classification of Dependable Real-Time Systems";
Betreuer/in(nen): P. Puschner, R. Kirner; Institut für Technische Informatik, 2007.

Implementing safety in real-time systems today requires time-consuming and cost-intensive certification procedures recommended by domainspecific safety standards. Additionally, meeting tight time-to-market deadlines in implementing increasing system complexity forces industry to find comprehensive ways to reduce the effort expended on developing system artifacts. This master’s thesis introduces a strategy for the development of dependable real-time systems that encapsulates the reuse potential of system behavior on the basis of requirements specifications. To this end, the platform-oriented concept of the model-driven architecture (MDA) is used to separate dependable system behavior on the basis of a platform-specific and platform-independent viewpoint. When it comes to integrating safety, a systematic development of requirements according to the RTCA/DO-178B guidelines helps to specify safety-critical behavioral aspects of a real-time system by using high-level and low-level requirements. Combining the viewpoint principles of the MDA with the systematic two-level requirements development according to RTCA/DO-178B is the basic strategy for the reuse of requirements, with a requirements classification pattern (RCP) dividing the dependable system behavior into four requirements classification windows (RCW). The assignment of requirements to RCWs is based on a platform-oriented analysis of system properties. The requirements classified in this thesis are stated in natural language. Each system property belongs to a platform layer, with a platform layer providing a manageable reusable insight of the system platform behavior. Thus, a platform layer, with its container-related characteristics, limits the scope of the RCP within the same technological domain. In order to demonstrate the practical relevance of the reuse strategy mentioned, an RCP developed for this thesis was applied to a set of sample software requirements of TTP-OS, a safety-critical, fault-tolerant real-time operating system developed according to RTCA/DO-178B as a certifiable software product for the aerospace industry. As the use of natural language for the specification of requirements often is ambiguous, so-called informal guidelines are used to support a platform-oriented property assignment decision. A reusable distribution reflects a majority of assigned requirements in the platform-independent RCWs. Changing requirements from being platform-specific to being platform-independent shows a reusedriven approach to developing requirements for dependable real-time systems.