On the complexity of single fault set diagnosability and diagnosis problems

The complexity of the single-fault (SF) set diagnosability and SF-diagnosis problems under the symmetric invalidation models is discussed. It is shown that the SF-diagnosis problem under both these models is co-NP-complete and the SF-diagnosability problem is also co-NP-complete under the asymmetric invalidation model. The SF-diagnosability problem is also studied under the symmetric-invalidation model and a polynomial time-complexity algorithm is presented. These results are in contrast with the corresponding t-diagnosability and t-diagnosis problems, which are known to have polynomial time-complexity algorithms.<>