Modelling and System Maintenance

This paper reports on recent work and directions in modern software ar-chitectures and their formal models with respect to software maintenance. The focus on maintenance attacks the most costly and frustrating aspect in dealing with large-scale software systems: keeping them up-to-date and responsive to user needs in changing environments. We employ mediators, autonomous modules which create information objects out of source data. These modules are placed into an intermediate layer, bridging clients and servers. A mediated architecture can reduce the cost growth of maintenance to a near-linear function of system size, whereas current system architectures have quadratic factors. Models provide the means for the maintainer to share knowledge with the customer. The customers can become involved in the maintenance of their task models without having to be familiar with the details of all the resources to be employed. These resources encompass the many kinds of databases that are becoming available on our networks.