If ?x is defined over some dense interval of ?t, then there are a finite number of points at which ?t is not continuous.
(Inherited-Facet-Value Slot-Value-Type Standard-Quantity D/Dt Piecewise-Continuous-Quantity) (<=> (Standard-Quantity ?X) (And (Everywhere-Continuous-Quantity ?X) (Value-Type ?X D/Dt Piecewise-Continuous-Quantity) (Value-Cardinality ?X D/Dt 1)))