A novel safety-critical system modeling approach: ternary decision diagram

In this paper safety-critical computer systems are broken down to functional modules. ternary decision diagram (TDD) is introduced to model these modules. Four cases of module construction techniques using TDD are discussed. For some dynamic modules that cannot be directly represented by TDD, the solution of the Markov model of the module provides the information for a single node TDD construction. The system level TDD is composed of the TDD of each functional module by the ORed combinatorial relationship. The system-coverage and the mean time to unsafe failure (MTTUF) are estimated via the system level TDD. An algorithm is proposed for the modular approach, and an example is utilized to verify the algorithm