The Functional Model Methodology (FMM)

The Functional Model Methodology (FMM) is a generic, graph-based methodology for modelling complex socio-technical systems. It emerged from functional modelling in Air Traffic Management (ATM), but its concepts are not tied to that domain. FMM represents a system as three distinct hierarchies: functions, information flows and organisational units. These are connected by typed, directed information links (flow edges). Among the established approaches considered in this paper (IDEF0/SADT, FRAM and model-based systems engineering frameworks), three features distinguish FMM. First, information flows are first-class elements with their own hierarchy, distinct from the functional decomposition but anchored in it level by level. Second, a single model is instantiated across an organisational hierarchy through inheritance and filtering, so that one generic model serves many organisations and operational units. Third, functional decomposition is governed by an explicit criterion based on enablers. This paper presents the concepts and modelling rules of FMM and summarises its application to MARIA, a generic functional model of an Air Navigation Service Provider (ANSP).