A method is provided for constructing at least a functional model of a complex system including a plurality of components. The method includes constructing the functional model of the complex system, including a hierarchized set of modelled functional components. Each of the functional modelled components is an instance of an object class belonging to a specific set of object classes. The specific set of object classes includes a “Functional Router” class, representing an abstract model of a dummy router, which describes a set of interconnections between at least two modelled functional components, each instance of the “Functional Router” class being called a modelled functional router. The functional model of the system includes at least one functional modelled router.