A query processing method for integrated access to multiple databases

  • Itaru Nishizawa
  • Atsuhiro Takasu
  • Jun Adachi
Advanced Database and Information System Methods 3
Part of the Lecture Notes in Computer Science book series (LNCS, volume 1134)


Multiple autonomous databases within a network system often contain similar information although their schemata are heterogeneous. This paper considers such heterogeneity and proposes a new method for achieving integrated access to multiple databases having similar schema. The method is based on the construction of a “virtual database (VDB)” by making use of null values and “virtual functional dependency (VFD),” which are formed over physically distributed component databases and applied to the query processing. We could obtain additional information relevant to the query and proved that this information is logically valid. When the VFD formed over a VDB is acyclic among the nodes that the query refers to, sound and complete answers can be efficiently calculated. We developed and implemented a bibliographic information retrieval system employing the schema integration method described herein such that integrated access is obtained for bibliographic information written in BibTEX.


Information Retrieval Query Processing Server Side Bibliographic Database Information Retrieval System 
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 1996

Authors and Affiliations

  • Itaru Nishizawa
    • 1
  • Atsuhiro Takasu
    • 2
  • Jun Adachi
    • 2
  1. 1.Department of Electrical EngineeringThe University of TokyoTokyoJapan
  2. 2.R&D DepartmentNational Center for Science Information SystemsTokyoJapan

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