gml:derivationUnitTerm

A set of gml:derivationUnitTerm elements describes a derived unit of measure.  Each element carries an integer exponent.  The terms are combined by raising each referenced unit to the power of its exponent and forming the product.
This unit term references another unit of measure (uom) and provides an integer exponent applied to that unit in defining the compound unit. The exponent may be positive or negative, but not zero.