Module mechanisms have received considerable theoretical attention, but the associated concepts of separate compilation and linking have not been emphasized. Anomalous module systems have emerged in functional and object-oriented programming where software components are not separately typecheckable and compilable. In this paper we provide a context where linking can be studied, and separate compilability can be formally stated and checked. We propose a framework where each module is separately compiled to a self-contained entity called a linkset ; we show that separately compiled, compatible modules can be safely linked together.