IEC 61360-2:2012 provides a formal model for data according to the scope as given in IEC 61360-1 and ISO 13584-42. It provides a means for the computer-sensible representation and exchange of such data, allowing for the implementation of dictionary systems dealing with data delivered according to either of the standards. This third edition cancels and replaces the second edition published in 2002, and its Amendment 1 (2003). It is a technical revision. It includes the following significant technical changes: - separation of concepts between characterization class and categorization class; - introduction of value constraints on classes and properties; - addition of various new subtypes for data types, including rational_type; - improvement on the representation of unit of measurement.