In the realm of medical decision-support systems, the term ''heuristic
systems'' is often considered to be synonymous with ''medical artific
ial intelligence systems'' or with ''systems employing informal model(
s) of problem solving''. Such a view may be inaccurate and possibly im
pede the conceptual development of future systems, This article examin
es the nature of heuristics and the levels at which heuristic solution
s are introduced during system design and implementation, The authors
discuss why heuristics are ubiquitous in all medical decision-support
systems operating at non-trivial domains, and propose a unifying defin
ition of heuristics that encompasses formal and ad hoc systems, System
developers should be aware of the heuristic nature of all problem sol
ving done Tn complex real world domains, and characterize their own us
e of heuristics in describing system development and implementation.