Abstract. We present a separate compositional analysis for objectoriented languages. We show how a generic static analysis of a context that uses an object can be split into two separate semantic functions involving respectively only the context and the object. The fundamental idea is to use a regular expressions for approximating the interactions between the context and the object. Then, we introduce an iterative schema for composing the two semantic functions. A first advantage is that the analysis can be parallelized, with a consequent gain in memory and time. Furthermore, the iteration process returns at each step an upper approximation of the concrete semantics, so that the iterations can be stopped as soon as the desired degree of precision is reached. Finally, we instantiate our approach to a core object-oriented language with aliasing.