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Using Constraints for Efficient Query Processing in Nondeterministic Databases
December 1995 (vol. 7 no. 6)
pp. 850-864

Abstract—Nondeterministic databases store disjunctive data using OR-objects. For example, data such as “Part#1 is implementable using Nickel or Cobalt” is stored as Implement(Part#1, o1) where Dom(o1) ={Nickel, Cobalt}; is the domain of the OR-object o1. 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 conforming if it satisfies all the FDs (functional dependencies) associated with the database. A database D is said to fully incorporate a set ${\cal F}$ of FDs if every possible world of D 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.

We first define a certain property called goodness of a class ${\cal D}$ of databases for a set ${\cal F}$ of FDs; goodness can be tested efficiently and enforced easily at schema design time.

For any class ${\cal D}$ of databases that is good for ${\cal F}$, we present: 1) a quadratic time algorithm for fully incorporating ${\cal F}$, 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 not 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.

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Index Terms:
Nondeterministic data, constraints, efficiency of query processing.
Kumar Vadaparty, Shamim Naqvi, "Using Constraints for Efficient Query Processing in Nondeterministic Databases," IEEE Transactions on Knowledge and Data Engineering, vol. 7, no. 6, pp. 850-864, Dec. 1995, doi:10.1109/69.476493
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