Uncertainty in rank join

  • Authors:
  • Ihab F. Ilyas

  • Affiliations:
  • University of Waterloo

  • Venue:
  • Search computing
  • Year:
  • 2011

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Abstract

At the core of the query processing engine of a search computing system are operators that retrieve, filter, join and aggregate results from theseWeb services. The main goal is to deliver relevant and multi-domain answers to user queries. In these scenarios, users usually expect a ranked list of relevant answers in contrast to the full answer set. Hence, ranking query results in the presence of uncertainty is a fundamental query processing challenge in search computing environments. Rank-join is a basic relational operator that reports the top-k join results as soon as possible, avoiding the expensive materialize-then-sort approach. Due to the early-out and pipelined nature of rank-join, it acts as one of the major building blocks in compiling execution plans for multi-domain queries (also knows as liquid queries). In this chapter, we discuss the implication of data uncertainty on the semantics and implementation of rank-join operators, and we survey some of the recent techniques to address these challenges.