Indexing the Solution Space: A New Technique for Nearest Neighbor Search in High-Dimensional Space

ÐSimilarity search in multimedia databases requires an efficient support of nearest-neighbor search on a large set of highdimensional points as a basic operation for query processing. As recent theoretical results show, state of the art approaches to nearest-neighbor search are not efficient in higher dimensions. In our new approach, we therefore precompute the result of any nearest-neighbor search which corresponds to a computation of the Voronoi cell of each data point. In a second step, we store conservative approximations of the Voronoi cells in an index structure efficient for high-dimensional data spaces. As a result, nearest neighbor search corresponds to a simple point query on the index structure. Although our technique is based on a precomputation of the solution space, it is dynamic, i.e., it supports insertions of new data points. An extensive experimental evaluation of our technique demonstrates the high efficiency for uniformly distributed as well as real data. We obtained a significant reduction of the search time compared to nearest neighbor search in other index structures such as the X-tree. Index TermsÐNearest neighbor search, high-dimensional indexing, efficient query processing, spatial databases, Voronoi diagrams.