title: Toward normative expert systems: Part II. Probability-based representations for efficient knowledge acquisition and inference.
abstract: We address practical issues concerning the construction and use of decision-theoretic or normative expert systems for diagnosis. In particular, we examine Pathfinder, a normative expert system that assists surgical pathologists with the diagnosis of lymph-node diseases, and discuss the representation of dependencies among pieces of evidence within this system. We describe the belief network, a graphical representation of probabilistic dependencies. We see how Pathfinder uses a belief network to construct differential diagnosis efficiently, even when there are dependencies among pieces of evidence. In addition, we introduce an extension of the belief-network representation called a similarity network, a tool for constructing large and complex belief networks. The representation allows a user to construct independent belief networks for subsets of a given domain. A valid belief network for the entire domain can then be constructed from the individual belief networks. We also introduce the partition, a graphical representation that facilitates the assessment of probabilities associated with a belief network. We show that the similarity-network and partition representations made practical the construction of Pathfinder.
authors.affiliation: Department of Computer Science, University of California, Los Angeles.
authors.forename: D E
authors.initials: DE
authors.lastname: Heckerman
authors.forename: B N
authors.initials: BN
authors.lastname: Nathwani
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D003936:Diagnosis, Computer-Assisted; D005103:Expert Systems; D006801:Humans; D008206:Lymphatic Diseases / Q000473:pathology*; D011336:Probability