Patrick C. Fischer

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Nondeterminism is one of the most elusive concepts in computing. In this paper we direct our efforts towards viewing nondeterminism as an additional resource at the disposal of time or space bounded Turing machine computations and study the classes of languages acceptable by these machines with <underline>restricted</underline> amounts of nondeterminism. (More)
Introduction. Weak multivalued dependencies (WlVDs) mre introduced by Jaeschke ind Scheck in order to characterize when twc NEST operations on different single attributes muld conmute [JSI. Thomas extended this result to nesting cn arbitrary structures and also gave a graph-theoretic characterization [Tl. In this paper we give additional characterizations(More)
Decomposition into Boyce-Codd Normal Form (BCNF) with a lossless join and preservation of dependencies is desired in the design of a relational database scheme. However, there may be no decomposition of a relation scheme into BCNF that is dependency preserving, and the known algorithms for lossless join decomposition into BCNF require exponential time and(More)
The procedure TANGENTS (P, m, p) accepts as its inputs a point p and a convex polygon P, given as a sequence of vertices beginning with m, also explicitly given. P is represented by means of an A VL tree T(P) modified so that each vertex Vi stores a pointer NEXT[vi] to the address of its successor Vi+l on the boundary of P. This modification is prompted by(More)