This document specifies a framework for representing data recorded in terminological data collections (TDCs). This framework includes a metamodel and methods for describing specific terminological markup languages (TMLs) expressed in XML. The mechanisms for implementing constraints in a TML are defined, but not the specific constraints for individual TMLs. This document is designed to support the development and use of computer applications for terminological data and the exchange of such data between different applications. This document also defines the conditions that allow the data expressed in one TML to be mapped onto another TML.