Finding two-tree-factor elements of tableau-defined monoids in time O(n3)
We consider the problem of finding elements in tableau-defined monoids. The solution of this problem is important to the minimization of restricted relational database queries. Although the problem has been shown to be NP-complete in general, many polynomial-time algorithms have been proposed for some subclasses of the general problem. The contribution of this paper is a new algorithm that finds elements with two-tree-factors in time O(n3). The number of elements that can be found in polynomial time is significantly increased by our algorithm as compared with the algorithms known so far.
Key wordsrelational database relational algebra query optimization tableaux
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