Experience in developing interoperations among legacy information systems using partial reverse engineering

At ICSM01 Johnson and Rosebrugh proposed a new methodology, based on formal specification techniques and partial reverse engineering, for developing interoperations among legacy information systems. The present brief paper reports on progress to date in designing such interoperations for major health informatics information systems. We describe briefly the methodology, argue for the value of partial reverse engineering and the benefits of the formal specification approach (based on category theory) that we use, and evaluate the methodology in two case studies. The main new result is the following. The ICSM01 paper correctly predicted that what was called there "full-duplex interoperation" would often provide more interoperability than is in fact required. We have discovered that the provision of full-duplex interoperability is indeed usually unnecessary, and it is costly because of the need to modify the legacy system. We proposed the development of "half-duplex interoperation" to avoid these costs, and we have since developed the half-duplex techniques. Nevertheless, the half-duplex techniques can still require some legacy system modification. Following recent work on partial information, we are developing an extension to the view based interoperation technique that avoids legacy system modification in over 92% of the cases we have investigated.