Techniques are provided for use in accordance with such systems as web sites operating electronic commerce (e-commerce) applications, interactive voice response (IVR) systems and workflow systems for providing automated monitoring of user activity and personalized action taking based on such activity, in accordance with an on-line decision support mechanism which combines formal and heuristic reasoning. In a web-based system, for example, the on-line decision support provided in accordance with the invention can be used in a wide variety of e-commerce applications requiring automated, real-time, intelligent interventions, including targeted promotions and discounts, assisting with navigation through self-help material, supporting dynamic price negotiations, and even selecting large portions of page content.