Abstract. We present a formal modelling approach using Abstract Data Types (ADTs) for developing large-scale systems in Event-B. The novelty of our approach is the combination of refinement and instantiation techniques to manage the complexity of systems under development. With ADTs, we model system components on an abstract level, specifying only the necessary properties of the components. At the same time, we postpone the introduction of their concrete definitions to later development steps. We evaluate our approach using a large- scale case study in train control systems. The results show that our approach helps reduce system details during early development stages and leads to simpler and more automated proofs.
Keywords: Event-B, refinement, abstract data types.