Software verification and validation: methodologies, tools and applications in space and aeronautical systems

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The use of programmable electronic systems has significantly increased over the years, even in control applications critical in terms of safety (e.g. in the nuclear, space, transport) fields.

The complexity of the software associated with these systems has grown exponentially with it.

Existing standards on functional safety recommend the implementation of Validation and Verification (V&V) processes to identify and minimize potential logical and software anomalies in control systems.

In this context, even if the purpose of the V&V activities is to adequately deal with the main security and reliability problems of the control systems and their software, the execution of the testing processes may be incomplete and ineffective unless directed, so systematically and according to rational priorities established according to risk minimization criteria, to adequately cover the set of conditions that the system can encounter during its operation, including non-nominal but still possible scenarios.

Further complications emerge when the traditional V&V methods are applied to control systems (model-based or adaptive) whose requirements are themselves represented by logical models.

With the increasing complexity of systems, the use of more sophisticated modeling tools (compared to traditional binary models, eg Reliability Block Diagrams, Event Trees, Failure Trees) becomes indispensable to adequately represent the dynamic and multi nature – status of functional failure modes associated with the execution of the control software. The main complexity factors concern the timing and synchronization of events and activities, control feedback, the different states of the system, the conditions of functional degradation and incipient failure.

The Dynamic Flowgraph Methodology (DFM) provides the analyst with one of the most advanced and effective structure and modeling elements for the representation and analysis of the dynamic interaction between a system and its control software.

During the seminar the basic features of the DFM methodology and the Dymondatm software tool will be introduced and discussed, and some applications in space and aeronautical systems created with the patronage of NASA (NASA Headquarter (NASA HQ), NASA Johnson Space Center ( NASA JSC) and NASA Ames Research center (NASA ARC)).

The seminar is organized in collaboration with NIER Ingegneria, a company adhering to the CRIT Accredited Suppliers Network, and ASCA Inc., a company that develops and applies systems engineering and safety and reliability assurance methods for government agencies and large US aerospace companies .


Sergio Guarro, president and chief-scientist of the research and development company ASCA Inc, is a recognized leader in the fields of “mission assurance” and systems security and reliability analyzes, with technical skills and experience developed through specific applications to the sectors aerospace, industrial and nuclear. He obtained the title of “Aerospace Fellow” in the Systems Engineering Division of Aerospace Corporation and in the field of research and development his activities include the formulation and demonstration of methodologies, processes and logical models for applications in the fields of security, diagnostics of systems, and risk analysis.