Since its birth in 1978, DIOGENE, the Hospital Information System of Geneva University Hospital has been constantly evolving, with a major change in 1995, when migrating from a centralized to an open distributed architecture.Since a few years, the hospital had to face health policy revolution with both economical constraints and opening of the healthcare network. The Hospital Information System DIOGENE plays a significant role by integrating four axes of knowledge

• medico-economical context for better understanding and influencing resources consumption

• the whole set of patient reports and documents (reports, encoded summaries, clinical findings, images, lab data, etc.) patient-dependent knowledge, in a vision integrating time and space

• external knowledge bases such as Medline (patient-independent knowledge)

• integration of these patient-dependent and -independent knowledges in a Case-Based Reasoning format, providing on the physician desktop all relevant information for helping him to take the most appropriate adequate decision.