1. An automated method for supporting a clinical diagnosis, comprising: storing a plurality of symptoms associated with a patient, the symptoms including characteristics of the patient, wherein each symptom is categorized as a present symptom, an absent symptom, or an open symptom; a processor establishing a multi-tier relationship between said plurality of symptoms and a plurality of diseases; the processor adjusting at least one weighting factor for at least one (a) at least one of said multi-tier relationships and (b) at least one of said symptoms, based on a knowledge model; and the processor building a ranking of diseases from said multi-tier relationship based on said weighting factors.