Searching in Metric Spaces by Spatial Approximation

  • Authors:
  • Gonzalo Navarro

  • Affiliations:
  • -

  • Venue:
  • SPIRE '99 Proceedings of the String Processing and Information Retrieval Symposium & International Workshop on Groupware
  • Year:
  • 1999

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Abstract

We propose a new data structure to search in metric spaces. A metric space is formed by a collection of objects and a distance function defined among them, which satisfies the triangular inequality. The goal is, given a set of objects and a query, retrieve those objects close enough to the query. The number of distances computed to achieve this goal is the complexity measure.Our data structure, called sa-tree (``spatial approximation tree''), is based on approaching spatially the searched objects. We analyze our method and show that the number of distance evaluations to search among n objects is o(n). We show experimentally that the sa-tree is the best existing technique when the metric space is high-dimensional or the query has low selectivity. These are the most difficult cases in real applications.