Integration of different components that compose enterprise Information System (IS) represents a big challenge in the IS development. However, it is indispensable in order to avoid fragmentation of the IS and redundancy between different IS applications. In this work we consider service-driven IS engineering as a prospective approach to deal with IS fragmentation and interoperability of different IS components. We introduce the notion of Information System Service (ISS) and propose a process model supporting legacy IS evolution by integration of new services. We claim that such an approach has to take into account a large number of integration situations and therefore has to be built by applying situational method engineering principals and defined as a collection of reusable method chunks.