BSI has published BS EN ISO 5459:2011, Geometrical product specifications (GPS). Geometrical tolerancing. Datums and datum systems, which is the British Standard equivalent of European Standard EN ISO 5459:2011 and International Standard EN ISO 5459:2011. The new British Standard was published on 31 August 2011 and replaces BS ISO 5459:1981.
BS EN ISO 5459:2011 specifies terminology, rules and a methodology for the indication and understanding of datums and datum systems in technical product documentation. In addition, explains the underlying concepts.
The standard defines the specification operator used to establish a datum or datum system (the verification operator can take different physical or mathematical forms and is not covered by this standard).
BS EN ISO 5459 provides tools to express location or orientation constraints, or both, for a tolerance zone, but it does not provide information about the relationship between datums or datum systems and functional requirements or applications.
BS EN ISO 5459:2011, ISBN 978 0 580 53481 2, is available from BSI priced at £196 plus carriage (or £98 for members of BSI).