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)))