This paper presents the results of an investigation into the types of
tests useful for automatically diagnosing combinational digital
devices. The diagnosis is bascd on a design model that allows
hierarchy in both the structure and the data of the device being
represented. A more general set of assumptions than is commonly
employed allows data values other than boolean values to be
diagnosed, and permits faults other than stuck-at thults to be found.
The design model, the assumptions, and the tests are represented in
SUffFLE, a language based on predicate calculus and specialized
Ibr digital systems.