2. An arrangement according to claim 1 , wherein said modelling means comprise first modelling means with computing means adapted to, from an input substantially non-formal description of a network management service, create a first formal model of the network management service comprising formal ontologies, and second modelling means adapted to, from an input written description of a probabilistic network model, create a formal probabilistic network description comprising formal ontologies to provide a second formal model.
2. An arrangement according to claim 1 , wherein said modelling means comprise first modelling means with computing means adapted to, from an input substantially non-formal description of a network management service, create a first formal model of the network management service comprising formal ontologies, and second modelling means adapted to, from an input written description of a probabilistic network model, create a formal probabilistic network description comprising formal ontologies to provide a second formal model. 10. An arrangement according to claim 2 , wherein the first formal model comprises a formal domain and behaviour model.