Rate is a property of a RepeatDose or ScheduleDose object.
This property defines
how fast a dose is given.
If you set the Rate property of a dose, you
must also specify the Amount property of the dose,
and set the DurationParameterName property to ''.
This is because the duration is calculated from the amount and rate.
Objects: RepeatDose, ScheduleDose
double (RepeatDose) or double
Nonnegative real number.
Default is 0 (RepeatDose)
or  (ScheduleDose).