Schema-Driven Evaluation of Approximate Tree-Pattern Queries

  • Torsten Schlieder
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2287)


We present a simple query language for XML, which supports hierarchical, Boolean-connected query patterns. The interpretation of a query is founded on cost-based query transformations: The total cost of a sequence of transformations measures the similarity between the query and the data and is used to rank the results. We introduce two polynomial-time algorithms that efficiently find the best n answers to the query: The first algorithm finds all approximate results, sorts them by increasing cost, and prunes the result list after the n then try. The second algorithm uses a structural summary -the schema- of the database to estimate the best k transformed queries, which in turn are executed against the database. We compare both approaches and show that the schema-based evaluation outperforms the pruning approach for small values of n. The pruning strategy is the better choice if n is close to the total number of approximate results for the query.


Data Tree Query Evaluation Conjunctive Query Data Node Original Query 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2002

Authors and Affiliations

  • Torsten Schlieder
    • 1
  1. 1.Institute of Computer ScienceFreie Universität BerlinBerlin

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