anslation of AML models to e.g. SDL models, UML models and high-level programming languages has been tested and is feasible. AML is also mature enough for standardization, although it is still not a standard. Summary Modelling languages for software and hardware modelling have reached a rather high level of maturity. The same cannot be said for systems modelling languages. An inherent problem is that such a language must be specific to a particular engi- neering domain in order to attract systems designers, and there are many domains to consider. Therefore, a classification of systems engineering domains to classify systems modelling languages is needed. To support the development of domain- specific modelling tools, a meta-language should be used to specify the semantics and syntax of domain-specific modelling languages. Having access to such a for- mal language specification also allows us to map the constructs of a domain-spe cific modelling language on the constructs of a software modelling languages, i.e. to apply a top-down approach on modelling languages in general. Formal system models that are produced and maintained in pre-design phases have an enormous potential for improving system engineering projects, with respect to process qualities such as productivity, system quality and leadtime. Projects that deal with complex systems and that rely only on the ad-hoc models and reports from very early phases often exhibit productivity, quality and leadtime figures that are far from satisfying. Formal system models can act as bridges between the very early phase and the design phase, and, if carefully modelled and maintained, can document most system design decisions that are taken before prod- uct design starts. SM&AML is partly a domain-specific modelling method that is focused on tele- com networks and systems, but can also be used as a modelling language for processing systems and real-time distributed systems in general. Models can be managed basically in two forms: as system models (by model management) o