Medical guidelines play an increasing role in selecting diag-nostic and therapeutic steps under the aspects of effectiveness, invasiveness, and costs. To work directly on patient data already available in electronic form, they should be integrated into a medical Information System. In order to develop a "medical guideline module" (MGM) managing and applying guidelines to patients, a "knowledge level" representation of guidelines is necessary which reflects the structure of medical knowledge and matches medical processes. Furthermore, a direct transformation to the "symbol level" is needed. We use a nested, frame-like structure on the knowledge level and show that a classification-based knowledge representation system (CBKRS) is principally well suited for the symbol level. To facilitate the usage and to be independent of a particular CBKRS, we introduce an intermediate level called "intelligent object system" (IOS). It is developed by augmenting a simple data model for describing complex objects with prototypes and implications as a means to classify objects and to draw inferences based on this Classification. Finally, the transformation of guidelines to prototypes and implications is described
