A Database Interface for Complex Objects

Marcel Holsheimer, Rolf A. de By, Hassan Aït-Kaci

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We describe a formal design for a logical query language using psi-terms as data structures to interact effectively and efficiently with a relational database. The structure of psi-terms provides an adequate representation for so-called complex objects. They generalize conventional terms used in logic programming: they are typed attributed structures, ordered thanks to a subtype ordering. Unification of psi-terms is an effective means for integrating multiple inheritance and partial information into a deduction process. We define a compact database representation for psi-terms, representing part of the subtyping relation in the database as well. We describe a retrieval algorithm based on an abstract interpretation of the psi-term unification process and prove its formal correctness. This algorithm is efficient in that it incrementally retrieves only additional facts that are actually needed by a query, and never retrieves the same fact twice.
Original languageEnglish
Place of PublicationCedex, France
PublisherDigital Equipment Corporation, Paris Research Laboratory
Number of pages34
Publication statusPublished - Mar 1993

Publication series

NamePRL Research Reports
PublisherDigital Equipment Corporation, Paris Research Laboratory


  • Relational databases
  • Complex object
  • Abstract interpretation
  • Psi-terms
  • Information retrieval
  • Inheritance
  • Logical Query Languages
  • Deductive databases


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