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Showing papers in "Journal of Computer and System Sciences in 1994"


Journal ArticleDOI
TL;DR: A new construction of a pseudorandom bit generator that stretches a short string of truly random bits into a long string that looks random to any algorithm from a complexity class C using an arbitrary function that is hard for C is presented.

921 citations


Journal ArticleDOI
Jarkko Kari1
TL;DR: It is shown that the reversibility problem is undecidable in case of two-dimensional CA, and it is proved that the corresponding surjectivity problem-the problem of deciding if the global function is surjective-is Undecidable for two- dimensional CA.

249 citations


Journal ArticleDOI
TL;DR: It is shown that most previously studied counting classes, including PP, C"=P, and Mod"kP, are ''gap- definable,'' i.e., definable using the values of GapP functions alone, and that there is a smallest gap-definable class, SPP, which is still large enough to contain Few.

183 citations


Journal ArticleDOI
TL;DR: A systematic comparison of several complexity classes of functions that are computed nondeterministically in polynomial time or with an oracle in NP shows that there exists a disjoint pair of NP-complete sets such that every separator is NP-hard.

180 citations


Journal ArticleDOI
TL;DR: The level-ancestor problem is considered and the Euler tour of the tree and the level of each vertex are given and the only change in result (1) above is that preprocessing time increases to O (log n ).

125 citations


Journal ArticleDOI
TL;DR: An algorithm is presented that performs any sequence of the following operations in the given time bounds that can insert a new pattern into the dictionary or delete a pattern from it.

97 citations


Journal ArticleDOI
TL;DR: A detailed analysis of the computational complexity of the different forms of closed world reasoning for various fragments of propositional logic is presented to draw a complete picture of the boundary between tractability and intractability of such a form of nonmonotonic reasoning.

93 citations


Journal ArticleDOI
TL;DR: This paper proposes two principles, justifiability and minimal undefinedness, for a three-valued model-theoretic approach to semantics of logic programs and deductive databases, which yields a declarative semantics, which is called the regular model semantics.

80 citations


Journal ArticleDOI
TL;DR: It is shown that for almost all oracles A, IP A ≠ PSPACE A, and the IPP = PSPACE result holds for all oracle worlds.

59 citations


Journal ArticleDOI
TL;DR: It is shown that optimally universal classes of hash functions are equivalent to resolvable balanced incomplete block designs and strongly universal classes are equivalentTo that end, known classes of combinatorial designs yield new, small, and efficient classes of universal hash functions.

57 citations


Journal ArticleDOI
TL;DR: An O(n^3) algorithm constructs a certain finite automaton that represents a canonical solution to a given set of type constraints and works equally well for recursive types.

Journal ArticleDOI
TL;DR: A general lower bound valid for all Boolean functions in the bounded error model is proved and it is shown that the (bounded error) probabilistic time complexity of Boolean functions on CREW PRAMs differs at most by a constant factor from the deterministic time complexity.

Journal ArticleDOI
TL;DR: This paper simplifies the proof of the main theorem, strengthens the result and uses it to obtain several new results, which implies that, up to relativization, some of the results are optimal.

Journal ArticleDOI
TL;DR: It is shown that every language in PSPACE, or equivalently, every language accepted by an unbounded round interactiveProof system, ha a 1-round, 2-prover interactive proof system with exponentially small error probability.

Journal ArticleDOI
TL;DR: This paper describes several parallel algorithms that solve geometric problems based on a vector model of computation-the scan model, and describes how to implement the CREW version of Cole's merge sort in O(lg n) calls to the primitives.

Journal ArticleDOI
TL;DR: It is proved that tree-generating top-down tree-to-graph transducers are equivalent to (total deterministic) macro tree transducers, which are transducers for which the translation of a subtree may depend upon its context.

Journal ArticleDOI
TL;DR: A conventional gift-wrapping algorithm for constructing the three-dimensional convex hull is revised into a numerically robust one that gives as the output a topologically consistent approximation to the true conveX hull.

Journal ArticleDOI
TL;DR: It follows that the communication complexity analogue of the Turing-complexity class FewP is equal to the analog of the class P, where P is the deterministic complexity of the function f.

Journal ArticleDOI
TL;DR: It is shown that the minimum possible number of edges in an n-superconcentrator of depth 3 is @Q(n log log n), whereas the minimum available number of edge numbers in a superconcentrators of depth 2 is @W (n(log n)^3^/^2) (and is O(n( log n) ^2)).

Journal ArticleDOI
TL;DR: The well-known perceptron learning algorithm is generalized to a k-ary perceptron algorithm with guaranteed convergence property and a k -ary winnow algorithm with a mistake bound which depends on this value and the ratio between the largest and smallest thresholds is presented.

Journal ArticleDOI
TL;DR: This work shows that by adding a modest amount of additional structure to database schemata, many important uniqueness results may be obtained, and establishes that under the condition that the schema is constrained by universal Horn sentences, there is a unique ultimate decomposition into a finite set of type restrictions.

Journal ArticleDOI
TL;DR: It is shown that every S-HH hypergraph language of bounded (hyper-)degree can be generated by a (separated) CFHG grammar, which implies that these two types of grammar generate the same class of graph languages of bounded degree, but incomparable classes of hypergraph languages.

Journal ArticleDOI
TL;DR: The monadic depth measure is introduced which is also shown to give rise to an infinite hierarchy of language families and it is shown that the monadic hierarchy is shifted by at most one level from the unrestricted depth hierarchy.

Journal ArticleDOI
TL;DR: The problem of computing medians in the outputs of metric Turing machines captures the computational complexity of P (#P) and PF(#P), the class of sets that are polynomial-time Turing reducible to #P functions.

Journal ArticleDOI
TL;DR: The answer is particularly simple: such an automaton may be invariant under all proper rotations that leave the underlying lattice invariant, but it cannot be invariants under the inversion that takes each configuration into its mirror image.

Journal ArticleDOI
Tadakazu Sato1
TL;DR: In this paper, the authors introduced group structured linear cellular automata which appear naturally in the process of finding their inverse automata and showed that the set of local maps of such automata forms a group with the star operation.

Journal ArticleDOI
TL;DR: Investigating connections between algorithmic identification in the limit of grammars from text presentation of recursively enumerable languages and standardizing operations on classes of recurring languages is the subject of this paper.

Journal ArticleDOI
TL;DR: If the degree bound k is greater than two, then the decision version of the problem is NP-complete, thus settling a conjecture of Aslam and Rivest.

Journal ArticleDOI
TL;DR: It is proved that three-head one-way DFA cannot perform string matching, that is, no three- head one- way DFA accepts the language L = x # y|x is a substring of y, where x, y @e {0, 1}*}.

Journal ArticleDOI
TL;DR: The power of the size-restricted criteria is characterized and it is used to prove that some classes of languages, which can be learned by converging in the limit to up to n + 1 nearly minimal size correct grammars, cannot be learned using this criterion even if these lattergrammars are allowed to have a finite number of anomalies per grammar.