This element defines the structure of a measure dimension for the NCube Instance. A value along the MeasureDimension is defined by a stack of references to one or more MeasureDefinitions found in the logical description of the NCube with each containing an attribute of orderValue which provides its value for use in the cell address (similar to the use of a CodeRepresentation of a Variable used as a conceptual dimension. This allows measures (whether one or several) to be handled in the same way as the conceptual dimension of the NCube in declaring a cell address. It is assumed that the value of the MeasureDimension is the last value in the address array. For example, for an NCube with 3 conceptual dimensions of rank 1 = Sex, rank 2 = Age, and rank 3 = Educational Attainment, plus a MeasureDimension. The cell address of 1,4,2,2 would indicate Code value of 1 for Sex, 4 for Age, 2 for Educational Attainment, and 2 for MeasureDimension. For systems translating to SDMX or an OLap structure DDI assumes that the MeasureDefinitionReference with the orderValue="1" is the equivalent of the PrimaryMeasure.