Introduction Recommendation Z.331 provides a summary of the functions which are to be controlled by means of MML. Each functional area in this list is to be specified in detail to allow the generation of function-related semantics. The use of such semantics in conjunction with the features provided by the Recommendations in Sections 2 and 3 allows the specification of the man-machine interface. In order to produce a detailed specification@ a formal method of working that provides a common approach is necessary. This Recommendation provides a methodology for such purposes. In order to assign properly the responsibility for the application of the methodology@ its application can be viewed as a two-stage process. The first stage involves the generation of function-related semantics. This stage is aimed primarily at those experts working in CCITT Study Groups who are responsible for developing Recomendations associated with functions to be controlled by MML. However@ it is recognized that the repertoire of such functions considered in CCITT Recommendations cannot cover the requirements of all Administrations or of all SPC systems. Therefore this stage is also aimed at Administrations@ private operating agencies and scientific/industrial organizations who may find it necessary to specify functions peculiar to their individual needs. The second stage of the application of the methodology involves the derivation of the actual man-machine interface using the semantics and the relevant features of Sections 2 and 3. This stage is the responsibility of Administrations@ private operating agencies@ and scientific/industrial organizations.