Engineering legacy information systems for internet based interoperation

The maintenance of legacy information systems is becoming increasingly common as needs for Internet based interoperation drive system changes. This paper outlines new techniques for achieving interoperability among legacy information systems, usually without making major changes to the legacy code. The techniques involved use a limited type of reverse engineering to establish a formal model of relevant parts of the legacy systems, and they use existing interfaces to communicate between the code written to support the reverse engineered models and the legacy code. Interoperation is then achieved using mathematical techniques to support common logically data independent views of the reverse engineered models. The paper is somewhat theoretical as it provides a detailed exposition of the new techniques, but the techniques themselves are currently being tested in industrial applications with considerable success, and they are based on a framework which has been used in a number of major consultancies.