A framework for expressing and combining preferences

The advent of the World Wide Web has created an explosion in the available on-line information. As the range of potential choices expand, the time and effort required to sort through them also expands. We propose a formal framework for expressing and combining user preferences to address this problem. Preferences can be used to focus search queries and to order the search results. A preference is expressed by the user for an entity which is described by a set of named fields; each field can take on values from a certain type. The * symbol may be used to match any element of that type. A set of preferences can be combined using a generic combine operator which is instantiated with a value function, thus providing a great deal of flexibility. Same preferences can be combined in more than one way and a combination of preferences yields another preference thus providing the closure property. We demonstrate the power of our framework by illustrating how a currently popular personalization system and a real-life application can be realized as special cases of our framework. We also discuss implementation of the framework in a relational setting.