1. An arrangement for network management and adapted to be provided in, associated with or in communication with, a network node to be managed, wherein the arrangement comprises, or is in communication with, modelling means adapted to, using non-formal descriptions, model network domain and behaviour using formal ontologies comprising inference capabilities by means of an inference engine, thus providing a formal ontology model describing domain and behaviour and annotating means adapted to add semantic information to the formal domain and behaviour ontology model, generating means adapted to, using said formal ontology model and said inference engine, elaborate an algorithm adapted to generate and update a probabilistic causal network graph structure representing the domain and its behaviour.