A General Theory for the Evolution of Application Models -- Full version

As has been argued in [Rod91] and [FOP92b], there is a growing demand for information systems, not only allowing for changes of their information base, but also for modifications in their underlying structure (conceptual schema and specification of dynamic aspects). In case of snapshot databases, structure modifications will lead to costly data conversions and reprogramming. The intention of an evolving information system ([FOP92a], [OPF94]) is to be able to handle updates of all components of the so-called application model, containing the information structure, the constraints on this structure, the population conforming to this structure and the possible operations. The theory of such systems should, however, be independent of whatever modelling technique is used to describe the application model. In this paper, we discuss a general theory for the evolution of application models. However, only conceptual aspects are considered, focus is on what evolution is, rather than on how to implement evolution in a database manegement system. In [PW93], an informal introduction to this theory is provided.