A Logic for Conditional Recommendation

A decision support system is a computerized system which utilizes knowledge about a particular application area to help decision makers by recommending suitable actions. An action is conditionally recommendable when a set of conditions associated with it is expected to be brought about in the state resulting from performing the action. Conditional recommendations occur frequently in practical decision-making contexts but their formal treatment is yet to be explored. Our approach is to develop a modal propo-sitional logic L cr for reasoning about conditional recommendations. The semantics of the logic is studied in terms of possible worlds where transition from one state to another is made by performing an action. The soundness and completeness of the logic is established. We also discuss the exploitation of L cr to formalize update and integrity constraint veriication in knowledge bases. 1 Motivation The formalization of conditional recommendation is important in the implementation of safety-critical systems, those decision support systems 3] where malfunction or operator error may give rise to severe injury, death or nan-cial/environmental catastrophe with the potential for legal liability. The work presented here arises from our involvement in a project addressing the technology and legal implications of knowledge-based decision support systems in safety-critical domains. To illustrate and motivate the abstract notions, we give examples in the domain of decision support in oncology, a speciic interest of one of the project partners. Because of the complexity of treatment performed and the amount of data captured during oncology trials, computerized decision support is essential. The safety-critical aspect arises from the narrow window between eecacy and toxicity of many of the treatments, but especially in chemotherapy 9]. A decision concerned with the selection of a particular treatment plan, or protocol, can be expressed as a high-level recommendation 6]: If the patient has operable bone cancer then consideration of treatment under protocol BO03 can be recommended. This kind of sentence has the general form If condition (the patient has operable bone cancer) holds in the present state of the knowledge base then an action (consideration of treatment under protocol BO03) can be recommended. Symbolically these sentences are of the form ! R()