iDistance Techniques

Synonyms

Query, Nearest Neighbor; Scan, Sequential

Definition

The iDistance is an indexing and query processing technique for k nearest neighbor (kNN) queries on point data in multi-dimensional metric spaces. The kNN query is one of the hardest problems on multi-dimensional data. It has been shown analytically and experimentally that any algorithm using hierarchical index structure based on either space- or data-partitioning is less efficient than the naive method of sequentially checking every data record (called the sequential scan) in high-dimensional spaces (Weber et al. 1998). Some data distributions including the uniform distribution are particularly hard cases (Beyer et al. 1999). The iDistance is designed to process kNN queries in high-dimensional spaces efficiently and it is especially good for skewed data distributions, which usually occur in real-life data sets. For uniform data, the iDistance beats the sequential scan up to 30 dimensions as reported in Jagadish et al. (2005...