Describes presentation of the data elements and maintenance of the directory. The standard data elements included are intended to facilitate interchange of data in international trade. These standard data elements can be used with any method for data interchange on paper documents as well as with other means of data communication. They can be selected for transmission one by one, or used within a particular system of interchange rules, e.g. the United Nations rules for Electronic Data Interchange for Administration, Commerce and Transport (UN/EDIFACT) published as International Standard ISO 9735.