Abstracts of Current Literature

S OF CURRENT LITERATURE The following research reports are available on request from: Advanced Computational Methods Center Computer Services Annex Building University of Georgia Athens, Georgia 30602 NEW REPORTS AND MEMOS 01-0004 A Programming Solution to Certain Problems with Loops in Prolog Nute, D. Representing transitive relations in the obvious way in Prolog results in unwanted loops. A programming solution to this problem is provided and limitations and possible extension of this solution to other looping problems is discussed. (Bound with 01-0001 and 01-0006.) 01-0006 A Further Note on Looping in Prolog Covington, M. In an earlier paper (01-0001) I proposed that looping in Prolog should be prevented by blocking all derivations in which the current goal matches a higher goal. This is too strong a constraint; it causes exhaustive searches to be incomplete. A better approach is to block all derivations in which the current goal matches a higher goal and is about to be evaluated using the same rule as was used to evaluate the higher goal. This is sufficient to block looping, and produce otherwise correct behavior, in all of the cases mentioned in the earlier paper. (Bound with 01-0001 and 01-0004.) 01-0007 A Non-Monotonic Logic Based on Conditional Logic Nute, D. A reasoning system is monotonic just in case it has the following property: whenever it infers a conclusion C from a set of assumptions S, it will also infer C from any larger set of assumptions containing S. Many AI researchers have stressed the need for non-monotonic reasoning systems, systems that can draw good conclusions from incomplete information and revise them as more information becomes available. Human beings often use defeasible rules in such reasoning. I will develop a system of formal logic for sentential versions of defeasible rules and compare this logic to other formal systems proposed as a foundation for non-monotonic reasoning. I will also discuss briefly a PROLOG program within which this logic is