AbstractThe growing complexity of models and the expanding availability of techniques do not fit adequately into the possibilities of Kendall’s famous classification. Even most ge-neralisations fail to cope with simulation models successfully. In the present paper it is tried to present an alternative shorthand notation that is able to give an adequate and unambiguous specification of most queueing models, both analytical and simulation models, at the cost of a somewhat more complex structure than Kendall’s. As such it should be suited to characterise simulation models with almost the same ease as simple analytical models can be defined, without sacrifising clarity to ambiguity.