Collaborative Preference Elicitation in a Group Travel Recommender System

When a recommender system requires users to specify their preferences explicitly and in detail, this process can become so tedious or impractical that the system is essentially inaccessible to some users. And where the recommendation is being made to a group, inaccessbility to one or more members may preclude use by the group as a whole. The present report describes work currently in progress on a way of facilitating preference specification which is especially applicable when a group of users is communicating asynchronously. Our preference elicitation interface explicitly encourages users to help each other with the preference elicitation task and to benefit from work that has been done by other members. The basic features of this approach are illustrated with examples, and some initial user testing is summarized. 1 Facilitating Explicit Preference Specification In some types of recommender systems, users are required to specify their preferences explicitly and in detail (see, e.g., Pu & Faltings, 2000, and the discussion of Tête-à-Tête in Maes, Guttman, & Moukas, 1999). This type of preference elicitation is often unnecessary if recommendations are to be based solely on the user’s general tastes, which may have been manifested in simpler ratings of objects, as in collaborative filtering. But when the user is making an important decision about a relatively complex object—such as an automobile or a vacation—he or she may have preferences and priorities that apply to this particular decision and may be only loosely related to longer-term preferences. One obvious problem with explicit, detailed preference elicitation is that it can be tedious and time-consuming. Another problem is brought to the foreground by the recent attention that has been given to the goal of universal accessibility (see, e.g., Stephanidis & Savidis, 2001): Some users may find it difficult or impossible to use such a recommender system at all, because of a lack of general computer sophistication, understanding of the domain in question, and/or time to deal with the complexities presented by the system. One possible approach to this problem is to tap a resource that has so far been underutilized in recommender systems for preference elicitation: other persons who are The research described here is being supported by the German Ministry of Education and Research (BMB F) under grant 01 IW 001 (project MIAU). in a good position to help the current user specify her preferences because they possess more relevant knowledge and/or time than the current user. A scenario in which it is particularly natural for users to help each other in this way is one in which a group of individuals who know each other are specifying their preferences concerning a decision that they intend to make together. For concreteness, consider the case of a geographically distributed family that is planning a vacation that they will take together. A recommender system should allow each member to specify preferences concerning numerous aspects of the vacation, ranging from the nature of the location to the specific facilities available there. Suppose that synchronous communication (e.g., via telephone or an on-line chat system) is impractical. Each member will then have to specify their preferences asynchronously. Suppose that at least one of the family members, to be called , would have difficulty specifying her preferences unaided. One or more of the other family members ( ) may be in an especially good position to help : The preferences of and may be largely similar, so that can get by largely by copying ’s preferences. In fact, may be willing to copy substantial parts of ’s preferences without even checking them in detail. Even if ’s own preferences differ from ’s, may know well enough to be able to make largely accurate suggestions for , which then needs only to check and perhaps modify. may trust to the extent of being willing to adopt many of ’s suggestions without careful checking. The process of communicating about preferences in these ways, in addition to increasing accessibility, can have the advantage of increasing the users’ understanding of each others’ preferences – which can be useful during a phase of negotiation about compromise solutions. In a situation like this, it would be natural for the group members to help each other with the preference specification process even if the system offered no specific support for such helping. For example, might simply ask to do the preference specification for her, perhaps checking the results before submitting them. But there are various ways in which a system can make this type of helping more efficient, reliable, and attractive to users. We are exploring such methods in the research described in this paper. 2 Exploratory User Studies In accordance with the principles of user-centered design, we began at an early stage presenting potential users of the travel planning system with mockups of possible user interfaces. The first issue of interest was whether our idea of helping users to help each other with preference specification would be well received by typical users. The persons we interviewed consistently confirmed that this basic conception seemed attractive to them—even if they were skeptical about the whole idea of planning a vacation through asynchronous communication. For example, within a family that comprised two parents, a 12-year-old boy, and a 6-year-old girl, we interviewed the mother and the son. They surprised us by volunteering the opinion that even the 6-year-old girl would be