George Markowsky

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Given an undirected distance graph G=(V, E, d) and a set S, where V is the set of vertices in G, E is the set of edges in G, d is a distance function which maps E into the set of nonnegative numbers and S⊑V is a subset of the vertices of V, the Steiner tree problem is to find a tree of G that spans S with minimal total distance on its edges. In this paper,(More)
In this paper we consider the question of how much space is needed to represent a set. Given a finite universe U and some subset V (called the vocabulary), an <underline>exact membership tester</underline> is a procedure that for each element s in U determines if s is in V. An <underline>approximate membership tester</underline> is allowed to make mistakes:(More)
Given a set, S, of Boolean n-vectors, one can choose k of the n coordinate positions and consider the set of k-vectors which results by keeping only the designated k positions of each vector, i.e., from k-projecting S. In this paper, we study the question of finding sets S as small as possible such that every k-projection of S yields all the 2 k possible(More)
Given partially ordered sets (posets) P and Q, it is often useful to construct maps g:P&#x02192;Q which are chain-continuous: least upper bounds (supremums) of nonempty linearly ordered subsets are preserved. Chaincontinuity is analogous to topological continuity and is generally much more difficult to verify than isotonicity: the preservation of the order(More)
Three famdies of strategies for orgamzmg an index of ordered keys are investigated It ~s assumed either that the index is small enough to fit m mam memory or that some superstrategy orgamzes the index into pages and that search within a page is being studied Examples of strategies within the three families are B-tree Search, Binary Search, and Square Root(More)