Universal and representative instances using unmarked nulls

  • Sushil Jajodia
Session 6 Data Bases
Part of the Lecture Notes in Computer Science book series (LNCS, volume 181)


Representative instances are important since in addition to the universal relation view they permit updates in the individual relations; if these updates are locally valid, then they do not violate global consistency. In this paper, we first give conditions under which we can construct a universal instance I which uses only one type of nulls (unmarked nulls) and whose total projections onto the relation schemes yield exactly the database relations. Then, we give a necessary and sufficient condition under which this I is actually a representative instance. Our conditions are simple and easily maintained.


Database System Relation Scheme Database Scheme Large Data Base Universal Relation 
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 1984

Authors and Affiliations

  • Sushil Jajodia
    • 1
  1. 1.Department of Computer ScienceUniversity of Missouri-ColumbiaColumbia

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