In this paper, we propose an object-oriented logical formalism to conceptionally model applications in an interoperable environment. Such an environment consists of heterogeneous and autonomous local (database) systems. Applications in such an environment use several resources and services. Their conceptual modelling involves re-specification of existing systems in terms of homogeneous views, modelling of behavior and system dynamics, modelling of logically distributed components in an open environment and the modeling of communication relationships and dependencies between components. We introduce a formal object-oriented language capable of dealing with these requirements and illustrate its use to model applications in an interoperable environment.