A property that is an enumerated property, typically unrelated to an algorithm, that may be extended in each successive version of the Unicode Standard.

• Examples are the Age, Block, and Script properties. Additional new values for the set of enumerated values for these properties may be added each time the standard is revised. A new value for Age is added for each new Unicode version, a new value for Block is added for each new block added to the standard, and a new value for Script is added for each new script added to the standard.