This International Standard specifies a framework designed to provide guidance on the basic principles for representing data recorded in terminological data collections. This framework includes a meta-model and methods for describing specific terminological markup languages (TMLs) expressed in XML. The mechanisms for implementing constraints in a TML are defined in this International Standard, but not the specific constraints for individual TMLs, except for the three TMLs defined in Annexes B to D. This International Standard is designed to support the development and use of computer applications for terminological data and the exchange of such data between different applications. It does not standardize data categories and methods for the specification of data structures which are specified in ISO 12620 and other related International Standards. This International Standard also defines the conditions that allow the data expressed in one TML to be mapped onto another TML and specifies a generic mapping tool (GMT) for this purpose (see Annex A). In addition, this International Standard describes a generic model for describing linguistic data.