To specify the required system behavior in a practical and efficient manner, the SCR method
uses mode classes. A mode class, whose values are modes, is an auxiliary variable that helps keep
the specification concise. Each mode defines an equivalence class of system states useful in
specifying the required system behavior. In SCR specifications, we often use the following prefixes
in variable names: “m” to indicate monitored variables, “mc” for mode classes, “c” for controlled
variables, “i” for input variables, and “0” for output variables.