doubleConstraintBaseType

The value is a bound for the quantity named by the element, a floating-point number such as 128.61. The required attribute @relationalOperator states how the quantity relates to it:

The example limits the calibrated airspeed of a point performance case to at most 128.61 m/s (250 kt) and the Mach number to at most 0.78.

<constraints>
    <calibratedAirSpeed relationalOperator="le">128.61</calibratedAirSpeed>
    <machNumber relationalOperator="le">0.78</machNumber>
</constraints>