On-line monitor design of finite-state machines

On-line monitoring is a useful technique for ensuring system reliability. By continuously supervising the system´s operation, a wide range of problems, such as physical defects, transient faults and design errors, can be detected A monitor M*´s behavior can be viewed as an abstraction of the target system M´s behavior, and can be represented by a homomorphic mapping from M to M*. We present a systematic procedure to select homomorphisms and measure their costs. Experimental results are also presented which quantify some basic trade-offs between area overhead and fault coverage.