Hierarchical Supervisory Control Under Partial Observation: Normality

Conditions preserving observability of specifications between the plant and its abstraction are essential for hierarchical supervisory control discrete-event systems under partial observation. Observation consistency local observation were identified as such conditions. To preserve normality, only is required. Although preserves normality levels normal specifications, that not normal, insufficient to guarantee supremal sublanguage computed on low level high coincide. We define modified consistency, which sublanguages different show verification (modified) PSpace -hard finite automata undecidable slightly more expressive models than automata. Decidability an open problem. Hence we further discuss two stronger conditions easy verify. Finally, illustrate example a railroad controller case study part MRI scanner.