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Issue No.06 - December (1995 vol.7)
pp: 850-864
ABSTRACT
<p><it>Abstract</it>—Nondeterministic databases store disjunctive data using OR-objects. For example, data such as “Part#1 is implementable using Nickel or Cobalt” is stored as <it>Implement</it>(<it>Part</it>#1, <it>o</it><sub>1</sub>) where <it>Dom</it>(<it>o</it><sub>1</sub>) ={<it>Nickel</it>, <it>Cobalt</it>}; is the domain of the OR-object <it>o</it><sub>1</sub>. A possible world of a database is obtained by replacing every OR-object by a member from its domain, and it is said to be <it>conforming</it> if it satisfies all the FDs (functional dependencies) associated with the database. A database <it>D</it> is said to <it>fully incorporate</it> a set $<tmath>{\cal F}</tmath>$ of FDs if every possible world of <it>D</it> is conforming. This paper studies the problem of preprocessing databases to achieve full incorporation, and also the problem of incrementally maintaining a database fully incorporated under insertions and deletions.</p><p>We first define a certain property called <it>goodness</it> of a class $<tmath>{\cal D}</tmath>$ of databases for a set $<tmath>{\cal F}</tmath>$ of FDs; goodness can be tested efficiently and enforced easily at schema design time.</p><p>For any class $<tmath>{\cal D}</tmath>$ of databases that is good for $<tmath>{\cal F}</tmath>$, we present: 1) a quadratic time algorithm for fully incorporating $<tmath>{\cal F}</tmath>$, 2) efficient algorithms for maintaining full incorporation under updates, and 3) lower-bounds for the algorithms of 1) and 2). Next, we show that, for classes of databases that are <it>not</it> good, the problem of full incorporation is, in general, coNP-complete. We also examine the complexity when OR-objects are restricted to have no more than two members, and obtain some interesting tractable algorithms, and intractability results.</p>
INDEX TERMS
Nondeterministic data, constraints, efficiency of query processing.
CITATION
Kumar Vadaparty, Shamim Naqvi, "Using Constraints for Efficient Query Processing in Nondeterministic Databases", IEEE Transactions on Knowledge & Data Engineering, vol.7, no. 6, pp. 850-864, December 1995, doi:10.1109/69.476493