Given a point query Q in multi-dimensional space, K-Nearest Neighbor (KNN) queries return the K closest answers in the database
with respect to Q. In this scenario, it is possible that a majority of the answers may be very similar to one or more of the
other answers, especially when the data has clusters. For a variety of applications, such homogeneous result sets may not
add value to the user. In this paper, we consider the problem of providing diversity in the results of KNN queries, that is,
to produce the closest result set such that each answer is sufficiently different from the rest. We first propose a user-tunable
definition of diversity, and then present an algorithm, called MOTLEY, for producing a diverse result set as per this definition.
Through a detailed experimental evaluation we show that MOTLEY can produce diverse result sets by reading only a small fraction
of the tuples in the database. Further, it imposes no additional overhead on the evaluation of traditional KNN queries, thereby
providing a seamless interface between diversity and distance.
Keywords Nearest Neighbor - Distance Browsing - Result Diversity