


Definition: 
An expression of measurement without units.

Context: 
A quantity is a value with an associated unit of measure. 32 Fahrenheit, 0 Celsius, $100 USD, and 10 reams (of paper) are quantities. Equivalence between two units of measure is determined by the existence of a quantity preserving onetoone correspondence between values measured in one unit of measure and values measured in the other unit of measure, independent of context, and where characterizing operations are the same.
Equivalent units of measure in this sense have the same dimensionality. The equivalence defined here forms an equivalence relation on the set of all units of measure. Each equivalence class corresponds to a dimensionality.
The units of measure "temperature in degrees Fahrenheit" and "temperature in degrees Celsius" have the same dimensionality, because for each value measured in degrees Fahrenheit there is a value measured in degrees Celsius with the same quantity, and viceversa. The same operations may be performed on quantities in each unit of measure. Quantity preserving onetoone correspondences are the wellknown equations C = (5/9)*(F  32) and F = (9/5)*(C) + 32.

Source
Publication: 
ISO/IEC FDIS 111791 "Information technology  Metadata registries  Part 1: Framework", March 2004.

Statistical
Theme: Methodological information (metadata) 
Glossary
Output Segments: 
SDMX

Created
on Monday, December 19, 2005 
Last
updated on Monday, December 19, 2005 












