Showing papers in "Journal of Computer and System Sciences in 1991"

TL;DR: It follows that such a complete problem has a polynomial-time approximation scheme iff the whole class does, and that a number of common optimization problems are complete for MAX SNP under a kind of careful transformation that preserves approximability.

TL;DR: In this paper, it was shown that expressing the Traveling Salesman Problem by a symmetric linear program requires exponential size, and the minimum size needed by a LP to express a polytope to a combinatorial parameter, point out some connections with communication complexity theory.

TL;DR: This paper proves the existence of a family of radius-2 networks on n vertices for which any broadcast schedule requires at least Omega((log n/ log log n)2) rounds of transmissions.

TL;DR: Deterministic and non-deterministic extensions of Datalog with fixpoint semantics are proposed, and their expressive power characterized, to overcome the limited expressive power available with purely declarative semantics.

TL;DR: This work presents a simple algorithm for emulating an N processor CRCW PRAM on an N node butterfly that improves the result of Pippenger by routing permutations with bounded queues in logarithmic time, without the possibility of deadlock.

TL;DR: The class IP is defined through the computational model of an interactive prover-verifier pair and it is shown that the first and second definitions are very restrictive.

TL;DR: The semi-unboundedness property leads to the definition of semi- unbounded fan-in circuit families and suggests new characterizations of LOGCFL on the following models: alternating Turing machines, nondeterministic auxiliary pushdown automata, and bounded fan- in Boolean circuits.

TL;DR: Kernel-LEAF is a logic plus functional language based on the flattening technique that is able to cope with partial functions and has a clean model-theoretic semantics, where the domains of the interpretations are the algebraic CPOs.

TL;DR: A new algorithm based on locking that permits more concurrency than existing commutativity-based algorithms is presented and it is proved that the algorithm satisfies hybrid atomicity, a local atomicity property that combines aspects of static and dynamic atomic algorithms.

TL;DR: Context-free hypergraph grammars generate the same string languages as deterministic tree-walking transducers because the number of tentacles of the nonterminals of the grammar is directly related to the crossing number of the transducer.

TL;DR: Inflationary DATALOG is proposed, an efficiently implementable cemantics for negation, based on inflationarv flxpoints, which is shown that, unfortunately, several compelling complexity-theoretic obstacles rule out its efficient implementation.

TL;DR: The expressive power of queries from the complex object calculus interpreted using semantics based on the use of arbitrarily large finite or infinite set of invented values is studied and an alternative semantics which yields a family of queries equivalent to the computable queries is considered.

TL;DR: A new algorithm based on ear decomposition for testing vertex four-connectivity and for finding all separating triplets in a triconnected graph is presented, which improves previous bounds for the problem for both the sequential and parallel cases.

TL;DR: In this article, the authors derive properties of infix and outfix codes which describe their relation to other classes of codes and determine their combinatorial structures, including maximal codes, maximal codes within these classes, the syntactic monoids of such codes, and the connection of these codes with binary relations on the free monoid.

TL;DR: An analogue to the classical serialisability theorem is established and used to derive simple proofs of correctness of two concurrency control algorithms for object bases, namely nested two-phase locking and nested timestamp ordering.

TL;DR: A simple combinatorial technique for constructing oracles that separate counting classes is developed and it is suggested that it will be difficult to resolve the unknown relationships among different counting classes.

TL;DR: A new definition of complex objects is introduced which provides a denotation for incomplete tuples as well as partially described sets and can be used constructively to infer consistent instances of conclusions and to refine complete instances of the hypothesis.

TL;DR: The results below apply to sequences generated by iteratively applying functions of the form f ( x ) = αx + β (mod p ) to a randomly chosen seed x and estimate the probability that a predetermined number of trials of an algorithm will fail.

TL;DR: It is shown that for an n processor network with a Constant number of connections and a constant number of buffers any deterministic pure source-oblivious strategy realizing all partial permutations requires Ω( n ) time.

TL;DR: Time-space tradeoffs for some algebraic problems in the branching program model, including convolution of vectors, integer multiplication, matrix-vector products, matrix multiplication, Matrix inversion, computing the product of three matrices, and computing PAQ where P and Q are permutation matrices are established.

TL;DR: A polynomial time isomorphism test for a class of groups, properly containing the class of abelian groups, given by multiplication tables or by generators and relators is described.

TL;DR: In this article, the authors consider the problem of learning an unknown language given a teacher which can only answer equivalence queries and study the learnability of subfamilies of regular languages.

TL;DR: It is shown that Ω(n( log n) 1 12 edges need to be examined by any randomized algorithm for determining any nontrivial monotone graph property.

TL;DR: It is shown semantically and operationally that complete and minimal sets of solutions under this equality theory always exist and can be generated by a special class of narrowing derivations.

TL;DR: A Voronoi-diagram is defined for a quite general subset of three-space which is characterized by specific axioms, and this diagram is one-dimensional and connected provided that the complement of the subset is connected.

TL;DR: An implicit data structure for storing n k -key records is described, which supports searching for a record, under any key, in the asymptotically optimal search time O (1g n ), in sharp contrast to an Ω(n 1− 1 k ) lower bound.

TL;DR: New techniques for deriving lower bounds on message complexity in asynchronous distributed computation combine the choice of specific patterns of communication delays and crossing-sequence arguments with consideration of the speed of propagation of messages, together with careful counting of messages in different parts of the network.

TL;DR: An algorithm is presented in the spirit of counting methods that correctly deals with cyclic data and has the same asymptotic running time as counting methods.

TL;DR: This note gives a proof of separation of arbitrary disjoint compact regions by two-layer McCulloch-Pitts(Mc-P) networks based on the theorem given in [3], and extends the result to arbitrary compact decision regions by the theorem of Hornik, Stinchcombe, and Wh ite.