Robust Development of Dependable Software Systems

The indissoluble bonds of computers and failures have produced a plurality of fault tolerant techniques to satisfy, potentially, any dependability requirement. As a consequence, the development of dependable systems is not based on inventing the mechanism that provides the desired dependability guarantees. Rather, it is based on selecting from the existing techniques the one that best meets the system's dependability requirements. Then, some codiication of the selected technique can be used as the search-key for retrieving from a repository of fault tolerant mechanisms the one that implements the selected technique. Hence, the development of dependable systems becomes a process that transforms a set of dependability constraints into a fault tolerant mechanism that meets them. The focus of our work is to ensure the rigorous development of dependable systems by creating a formal basis for the aforementioned selection process. More precisely, this formal basis consists of: a system model in terms of states and actions, which permits the speciication of dependability properties in temporal predicate logic; a reenement relation for dependability properties, a reenement relation for system speciications, and their correlation. a means that derives automatically the architectural impact of a dependability property to a system speciication. a classiication scheme, which captures the property and speciication reenement relations. This scheme organizes the contents of a repository of fault tolerant mechanisms, which results in accelerating their retrieval. The practical contribution of this work is assessed in the Aster development environment. The formal basis is adapted to Aster speciicities. In addition, a CASE tool is presented that uses the classiication scheme to perform the analysis of dependability requirements. The CASE tool is integrated with the Aster toolkit, replacing the standard Aster tool in the retrieval of fault tolerant mechanisms. The analysis results are also used to provide guidelines for incorporating the selected fault tolerant mechanism in the system structure. While not innovative in its parts since it employs well known techniques from the elds of formal speciications, requirements analysis, software architecture, and software reuse, the originality of this work lies in the combination of existing software technologies for the beneet of system development. The development robustness is guaranteed by the rigorous analysis and the correct reenement of the system's dependability requirements. Construction robuste de systtmes logiciels ssrs de fonctionnement RRsumm : Les liens indissolubles entre les ordinateurs et les ddfaillances ont conduit l'inven-Des moyens pour ddriver automatiquement l'impact architectural d'une propriitt de ssrett …