A flexible approach to client-server computing.

The number of standards for client-server computing almost equals the number of client-server applications. Although there are some standardization efforts, there is hardly any experience with applying these solutions to (medical) practice. The layering approach of the integration architecture HERMES anticipates the inclusion of commercial standards (when available and evaluated); it currently supports already the development of client-server applications. The toolkit provides support for the development of the communication between client and server through a callback mechanism. Stubs created with the HERMES toolkit contain a number of built-in callbacks that manage sessions between clients and services. An important feature of HERMES is the ability to include existing legacy systems as if they are true open services. In this way, the growth path from stand-alone to client-server computing can be shortened and the implementation of the client-server architecture can begin immediately. Moreover, the existing legacy systems remain available as a stand-alone solution for daily practice. Clients and services are connected through the HERMES kernel. This kernel uses a database to find the best server match for a request from a client. Moreover, it completes requests with mandatory data and tries to optimize performance. Special features are included to minimize the memory burden of the session-oriented client-server model. Currently, a system for the outpatient clinic cardiology, occupational health care, and clinical data analysis is available.