lansky@VENICE.AI.SRI.COM (Amy Lansky) (10/30/87)
DEFAULTS AND CONJECTURES: HYPOTHETICAL REASONING FOR EXPLANATION AND PREDICTION David Poole (dlpoole%watdragon.waterloo.edu@relay.cs.net) Logic Programming and Artificial Intelligence Group University of Waterloo 11:00 AM, MONDAY, November 2 SRI International, Building E, Room EJ228 Classical logic has been criticised as a language for common sense reasoning as it is monotonic. In this talk I wish to argue that the problem is not with logic, but with how logic is used. An alternate way to use logic is by using theory formation; logic tells us what a theory implies, an inconsistency means that the theory cannot be true of the world. I show how the simplest form of theory formation, namely where the user supplies the possible hypotheses, can be used as a basis for default reasoning and model-based diagnosis. This is the basis of the "Theorist" system being built at the University of Waterloo. I will discuss what we have learned from building and using our system. I will also discuss distinctions which we have found to be important in practice, such as between explaining observations and making predictions; and between normality conditions (defaults) and abnormality conditions (prototypes, conjectures, diseases). The effects of these distinctions on recognition and prediction problems will be presented along with algorithms, theorems and examples.