Using Semiouterjoins to Process Queries in Multidatabase Systems.

Hai-Yann Hwang, Umeshwar Dayal, Mohamed G. Gouda: Using Semiouterjoins to Process Queries in Multidatabase Systems. PODS 1984: 153-162

@inproceedings{DBLP:conf/pods/HwangDG84,
  author    = {Hai-Yann Hwang and
               Umeshwar Dayal and
               Mohamed G. Gouda},
  title     = {Using Semiouterjoins to Process Queries in Multidatabase Systems},
  booktitle = {Proceedings of the Third ACM SIGACT-SIGMOD Symposium on Principles
               of Database Systems, April 2-4, 1984, Waterloo, Ontario, Canada},
  publisher = {ACM},
  year      = {1984},
  isbn      = {0-89791-128-8},
  pages     = {153-162},
  ee        = {http://doi.acm.org/10.1145/588011.588033, db/conf/pods/HwangDG84.html},
  crossref  = {DBLP:conf/pods/84},
  bibsource = {DBLP, http://dblp.uni-trier.de}
}

Abstract

A multidatabase system provides a logically integrated view of existing, possibly inconsistent, databases. Logical integration is achieved primarily through the use of generalization, which can be modelled algebraically as a sequence of outerjoin and aggregation operations. Conventional distributed query processing techniques are inadequate for processing queries over views defined by outerjoins and aggregates. In a conventional distributed database system, selections and projections are inexpensive to process; hence joins have been the focus of most previous research. In a multidatabase system, however, even selections and projections can be as expensive as joins. The semiouterjoin operation can potentially reduce query processing costs. In general, there may be many different strategies based on semiouterjoins for processing a given query. The query optimization problem is to choose the most profitable of these strategies. This paper studies the query optimization problem for selection and projection queries. It develops linear-time solutions to the problem, and then extends these solutions to provide heuristics for joins and conjunctive queries.

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Proceedings of the Third ACM SIGACT-SIGMOD Symposium on Principles of Database Systems, April 2-4, 1984, Waterloo, Ontario, Canada. ACM 1984, ISBN 0-89791-128-8
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References

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