UnitOfMeasure   A standard of measurement for some dimension. For example, the Meter is a UnitOfMeasure for the dimension of length, as is the Inch. There is no intrisic property of a UnitOfMeasure that makes it primitive or fundamental; rather, a systemofunits (e.g. SystemeInternationalUnit) defines a set of orthogonal dimensions and assigns units for each  PhysicalQuantity  MeasureFn  SubtractionFn  (=> (and (instance ?REL RelationExtendedToQuantities) (instance ?REL BinaryRelation) (instance ?NUMBER1 RealNumber) (instance ?NUMBER2 RealNumber) (holds ?REL ?NUMBER1 ?NUMBER2)) (forall (?UNIT) (=> (instance ?UNIT UnitOfMeasure) (holds ?REL (MeasureFn ?NUMBER1 ?UNIT) (MeasureFn ?NUMBER2 ?UNIT)))))
