Date of Original Version



Working Paper

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Abstract or Description

Embedded systems of today pose difficult dependability challenges. Hardware and software requirements as well as human interface components all contribute to or detract from the overall dependability of a system. Assigning a ‘dependability number’ to a system is becoming increasingly subjective due to the confluence of these three areas. In particular it is important to go beyond composing individual component reliability predictions, and additionally consider factors such as ease of user workaround in the face of a partial system failure. We suggest evaluating the opportunity for success of a user’s mission in terms of flexibility in selecting a series of tasks to accomplish a specified goal. With this user perspective, we create graphs to represent user states and tasks, and explain how some aspects of system dependability can be assessed through standard graph analysis techniques.