ASME Y14.5 : Dimensioning and Tolerancing

The physical boundary used to establish a simulated datum from a specified datum feature. NOTE: For example, a gage, a fixture element, and digital data (such as machine tables, surface plates, a mandrel, or a mathematical simulation) are not true planes, but are of sufficient quality that the planes derived from them are used to establish simulated datums. Datum feature simulators are used as the physical embodiment of the true geometric counterparts during manufacturing and inspection. See ASME Y14.43.

See Also:

Datum, Datum Feature, Geometric Element