Free-text forms of medical guidelines that are used in medical care are often cumbersome and difficult to memorize. Therefore a system that is able to present guidelines in a user-friendly manner has been designed. Guidelines are at first formalized by means of the popular GLIF3 model. Subsequently, the GLIF3 model is coded in XML. The system uses patient data and an XML-coded GLIF3 model graph evaluating the conditions of decision steps. If some conditions cannot be evaluated, (due to the unavailability of required data items), the system stops and highlights a branch from the root of the decision tree to the final step. Then, the user can input missing data into the system so that the system can continue to provide visualization. Thus, the presentation of guidelines is data-driven, making its use easier. The visualization system and the Electronic Health Record can be integrated in a system that can, during examination of a patient, suggest subsequent medical actions according to medical guidelines. Such a system has been designed and is now under development.