Static discipline
In a digital circuit or system, static discipline is a guarantee on logical elements that "if inputs meet valid input thresholds, then the system guarantees outputs will meet valid output thresholds", named by Stephen A. Ward and Robert H. Halstead in 1990, but practiced for decades earlier.
The valid output thresholds voltages VOH and VOL, and valid input thresholds VIH and VIL, satisfy a robustness principle such that
with sufficient noise margins in the inequalities.