Semi-discrete events and models in categorical language

Some problems related to discrete event simulation and model validation are discussed. The validity of models with simultaneous events is discussed. The basic concepts of the theory of categories are recalled and applied to model construction process. The language of the theory of categories is used to treat some problems in modelling and simulation of discrete event, namely the ambiguity that may appear when simultaneous events occur. It is pointed out that the theory of categories may be useful as a unified language for model description. In particular, the categorical point of view can be useful while treating the model validity. Using this language we can get a high level of abstractions in model building.