Evolving Logical Specification in Information Systems

Traditional logic-based speci cation approaches x the structure and the dynamics of an object system at speci cation time. Information systems are applications with a very long life-time. Therefore, object and speci cation evolution to react on changing requirements is a relevant aspect of describing information systems as object societies. We present a logical speci cation framework for evolving objects based on the concepts of object developed for the languages Troll and Gnome and the underlying temporal logic OSL. The syntactic notion of object descriptions is extended to explicitly manipulate temporal axioms during behaviour evolution. An extension of OSL called dyOSL establishes a logical framework where basic temporal formulae are evaluated by a second logical layer. dyOSL explicitly manipulates state-dependent sets of temporal formulae to model evolution of object axioms. Syntax and semantics of dyOSL are given together with a translation of the specication language constructs into dyOSL. The corresponding proof theory is discussed together with guidelines for formally certifying object properties. Additionally, we show the use of the formalism for some speci c information system scenarios. Acknowledgments We are grateful to Amilcar Sernadas for discussing with us this di cult problem. Work presented here was partially supported by PRAXIS XXI Project 2/2.1/MAT/262/94 SitCalc, ESPRIT III Working Group 8319 ModelAge, ESPRIT IV Working Group 22704 ASPIRE, and ESPRIT IV Working Group 23531 FIREworks.