This paper defines strongly language disjoint (SLD) checkers. SLD checkers are to sequential systems what strongly code disjoint checkers are to combinational systems. SLD checkers are the largest class of checkers with which a functional system may achieve the TSC goal. Self-checking sequential systems are first addressed, then formal definitions of SLD checkers are given. The next point is the design of SLD checkers based on regular combinational self-checking components.
IEEE Transactions on Computers. New York. vol. 37, n. 6 (june 1988), p. 745-748