Structure preserving modeling for safety critical systems

To warrant the functionality of safety critical circuits and systems, underlying functions have to be modeled in a fashion that preserves real-world structure. That means, it must be ensured that the formally derived functions of the real-world structure should be in consistent conformance with the functions generated by the structure itself. Conversely, from safety-related aspects, it is fatal, when the modeled functions behave different from their functions in reality. Thus, although structure preserving modeling is safety-relevant, the state of the art does not consistently handle the formal derivation and modeling of functions. Particularly this happens at asynchronous feedbacked structures, especially in favor of simplification and later optimization. Looking at a very elementary asynchronous feedback logic, we show that this problem of inconsistency is omnipresent, and that our demand for consistency can not be warranted by the state of the art methods. We propose a new modeling methodology that is capable to preserve the structure of asynchronous feedback.