This paper presents the novel Process Oriented Medical Information System Architecture (PROMISE) which has been developed in detail especially for the requirements of hospital information system engineering processes. The architecture is given in three colums and three layers along the following three dimensions: business process modeling, process specification and engineering. The heart of the architecture is a purpose-built framework for hospital information systems called PROSIGHT whose implementation can be used easily as a workbench. The single components can be customized according to detailed modeled hospital business processes which form in common a complete hospital information system. Any other framework can be used instead PROSIGHT if it can be used as a reference hospital information system in the same manner. Although the PROMISE architecture is presented in common with the given framework it can be seen as an open architecture. The hospital information system engineering process comprising the development as well as the adaptation process for a certain hospital will be skeched out.