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Showing papers in "Journal of Computer and System Sciences in 1989"


Journal ArticleDOI
L. P. Chew1
TL;DR: It is shown that there is a planar graph G on S with the property that for any points A and B of S there exists an A-to-B path along edges of the graph with path length equal to the straight-line distance between A and A.

311 citations


Journal ArticleDOI
TL;DR: This paper shows how to preprocess the polygon so that, given two query points p and q inside P, the length of the shortest path inside thepolygon from p to q can be found in time O(log n).

271 citations


Journal ArticleDOI
TL;DR: The framework defined in this paper enables us to prove precise statements about what an encrypted instance hides and what it leaks, in an informationtheoretic sense, as well as describe encryption schemes for some well-known functions.

212 citations


Journal ArticleDOI
Pierre America1, Jan Rutten
TL;DR: This paper presents a technique by which solutions to reflexive domain equations can be found in a certain category of complete metric spaces, and shows that for a large class of functors, including function space constructions, these conditions are satisfied, so that they are guaranteed to have a unique fixed point.

194 citations


Journal ArticleDOI
TL;DR: It is shown that the strong exponential hierarchy collapses to P NE, its Δ 2 level, using the use of partial census information and the exploitation of nondeterminism.

164 citations


Journal ArticleDOI
TL;DR: Two versions of probability amplification lemmas are presented wich connect probabilistic complexity classes with nonuniform classes and the “quantifier simulation” technique is introduced which allows assertions that hold with high probability to be expressed by two alternating quantifiers.

137 citations


Journal ArticleDOI
Jim Kadin1
TL;DR: The main result is that if there exists a sparse set S ϵ NP such that co-NP ( NPs, then the polynomial hierarchy (PH) is contained in PNP[O(log n], and it is shown that this collapse is optimal.

90 citations



Journal ArticleDOI
TL;DR: Primary computations over relational structures give rise to computable relations definable by formulas of the form (∀ relations) (∃ objects ) ϕ with ϕ quantifier free, and several known descriptive characterizations of complexity classes ensue.

59 citations


Journal ArticleDOI
Eric Allender1
TL;DR: In this paper, it is shown that if secure generators exist, then there are fast deterministic simulations of probabilistic algorithms; the nature of the simulations and the class of algorithms for which simulations can be exhibited depends on the notion of security which is assumed.

44 citations


Journal ArticleDOI
TL;DR: A class of new applications of the nested dissection method is presented, this time to path algebra computations, where the path algebra problem is defined by a symmetric matrix A whose associated undirected graph G has a known family of separators of small size s ( n ) (in many cases of interest).

Journal ArticleDOI
TL;DR: A direct, simple and general parallel algorithm is described for the preprocessing of a planar subdivision for fast (sequential) search and applications to the manipulation of convex polyhedra are described.

Journal ArticleDOI
TL;DR: An algorithm is presented for computing geodesic furthest neighbors for all the vertices of a simple polygon, where geode denotes the fact that distance between two points of a polygon is defined as the length of an Euclidean shortest path connecting them within the polygon.

Journal ArticleDOI
TL;DR: A linear-time algorithm is given that detects many recursive definitions in deductive database systems, and specifies a useful subset of recursive definitions for which the algorithm is complete, and can be used to optimize a recursive definition, and improve the efficiency of the compiled evaluation algorithms.

Journal ArticleDOI
TL;DR: An experimental study on approximation of continuously distributed geometric objects by equations with integer coefficients, which considers three heuristic methods: a naive method, a method based on the continued fraction theory, and a method using the basis reduction technique.

Journal ArticleDOI
TL;DR: The concept of a complete test database is defined, the notion using Armstrong databases is characterized, and two constructions for producing complete test databases are given.

Journal ArticleDOI
TL;DR: This work develops a method of analysis based on dent diagrams for orthogonal polygons and is able to show that Keil's O(n2) algorithm for covering horizontally convex polygons is asymptotically optimal, but it can be improved to O( n) for counting the number of polygons required for a minimal cover.

Journal ArticleDOI
TL;DR: The expressive power of minimalism and positivism is compared, in both static and dynamic contexts, and shows that positivism and minimalism are “non-monotonic” in different ways.

Journal ArticleDOI
TL;DR: A necessary and sufficient condition for a “sideways information passing” method for evaluating Horn clause queries in the presence of monotonicity constraints on the database relations is given and a related condition is proved for the case of downward finite domains.

Journal ArticleDOI
TL;DR: A deterministic polynomially time-bounded reducibility ⩽rP and its nondeterministic analogue ⩼rNP provide a positive relativization of this problem if P = NP is equivalent to P · r(B) = NP · r (B) for all oracle sets B.

Journal ArticleDOI
TL;DR: The problem of testing if a network has a given ‘property’ whose testing requires an exponentially large number of input-output tests is (apparently) intractable, i.e., it is not in P unless NP = co-NP, and the NP-completeness or the coNP- completeness of some fundamental network testing problems is shown.

Journal ArticleDOI
TL;DR: It is shown that P = NP implies the existence of a recursively enumerable set A which is minimal for the honest polynomial reducibilities, and shows that P ≠ NP if the degree structures of the honest and nonhonest reducibility on the recursive enumerable sets are isomorphic.

Journal ArticleDOI
TL;DR: The optimal lower bounds W ( n 3 ) and gW(n 5 2 ) are proved for the recognition of specific 2-dimensional languages on 2-AM(1) and 2- AM( k ), respectively.

Journal ArticleDOI
TL;DR: The Low Degree Subgraph Problem is defined and shown to be NP-complete, whereas, the “complementary” problem for high degree subgraphs was previously shows to be P-complete.

Journal ArticleDOI
TL;DR: The theory of attainability is developed, which is used to give intuition about the structure of minimal forced wins for either player, and about the “difficulty” of the game.

Journal ArticleDOI
TL;DR: It is shown that such an array (with the nodes capable of doing simple arithmetic and logical operations) can efficiently solve linear as well as some nonlinear recurrence equations.

Journal ArticleDOI
TL;DR: It is shown that the conditions on when it is safe to forget (and remove) a completed transaction in several versions of conflict-graph-based schedulers can be applied repeatedly and analyzed their complexity.

Journal ArticleDOI
TL;DR: The deterministic category rearrangement problem is NP-complete (for run length encoding compression methods) via a reduction to the rectilinear traveling salesman problem and the probabilistic model has the form of a double pipe organ.

Journal ArticleDOI
TL;DR: The standard serializability criterion is extended to this model and it is shown that for regular transactions the set of serializable computations is regular.

Journal ArticleDOI
TL;DR: It is shown that testing fd-acyclicity can be done in polynomial time and an interesting special case is when the relation schemes are closed under the functional dependencies of the database scheme.