Showing papers in "Journal of Computer and System Sciences in 1987"

TL;DR: It is shown that such a minimum edge set can be determined in O ( k L|V| 4 ( k |V| + |E|) time for any graph G = (V E ) and any fixed k≧2 , where L = min { k, | V |}

TL;DR: The properties of a simple and natural notion of observational equivalence of algebras and the corresponding specification-building operation are studied and behavioural equivalence is treated as an important special case.

TL;DR: The Amalgamation Theorem states that graph derivations which respect the given associations can be amalgamated to a single derivation via the “amalgamated” production.

TL;DR: A new notion of transition systems is introduced, where states are sets of processes and transitions specify which processes stay idle, and a notion of observations based on partial orderings, called concurrent histories, is defined on computations.

TL;DR: Upper bound time-space trade-offs are established for sorting and selection in two computational models for machines with input in read-only random access registers and on a read- only tape.

TL;DR: Initial structures are characterized in terms of their genericity properties and a syntactic characterization of first-order theories admitting initial .structures is given to explain why Horn formulas have gained such a predominant role in various areas of computer science.

TL;DR: An algebraic specification concept for modules in software engineering is introduced which includes, in addition to a parameter and body part, explicit import and export interfaces and composition and union are studied in detail.

TL;DR: It is shown that the nonemptiness of complement problem for deterministic Buchi automata (i.e., whether L(Γ)′ = ⊘) is solvable in polynomial time, and whether L = e may be determined in time O(e2), where e is the number of edges of Γ.

TL;DR: In general, it is found that both respects are dominated by the extent to which the capabilities of synchronization and (unbounded counting are enabled in the communication scheme.

TL;DR: This paper shows that the notion of bisimulation for a class of labelled transition systems (the class of nondeterministic processes) may be restated as one of “reducibility to a same system” via a simple reduction relation.

TL;DR: A common framework for solving several VLSI river routing problems is developed and an O(n) time algorithm for the optimum offset problem is developed that improves upon the best previously known O( n log n ) time bound.

TL;DR: Algorithms of lower complexity are obtained for solving the problem of whether or not a given finite string-rewriting system R is confluent on a given congruence class [w]R, when only length-reducing systems are considered.

TL;DR: A new combinatorial property is given which characterizes context-free group languages: they are “locally primary,” which means that the cylinder generated by the group languages is included in the family of NTS languages.

TL;DR: A calculus for the classes of deterministic flowchart schemes with respect to the strong equivalence relation, similar to the calculus of theclasses of polynomials withrespect to the reduction of similar terms is given.

TL;DR: It is demonstrated that, for the Verso model, nesting relations not only leads to a more natural data representation but also leads to more succinct and efficient data manipulation.

TL;DR: A notation for defining functions or procedures in such a way that their termination is guaranteed by the scope rules is proposed, which uses an extension of case expressions.

TL;DR: A C n lower bound for read-once-only branching programs computing an explicit Boolean function that computes the parity of the number of triangles in a graph on ν vertices is given.

TL;DR: This paper shows that Σ 2 SPACE ( n ) is closed under complement, where Σ k SPACE( n ) denotes a class of languages accepted by linear space-bounded alternating Turing machines whose initial state is existential and which make at most k − 1 alternations, for each k > 0 .

TL;DR: A heap (priority queue) is a data structure for representing a set of items, each item having an associated numerical value, which facilitates such operations as insertion, deletion, merge (union), and findmin, and it is observed that when the frequency of findmin operations is small relative to thefrequency of other operations, then certain implementations of heaps perform better than logn per operation.

TL;DR: A process concept is introduced similar to that of Staples and Nguyen, but more general, where processes are represented by the sets of scenarios they areable to realize and communicate via shared places.

TL;DR: This work develops a strictly algebraic theory of recursion schemes with second-order substitutions that gives a semantics for nondeterminism and for process algebras.

TL;DR: A combinatorial (“functional”) notation for the sequential and parallel composition as well as for a feedback operator for those agents is introduced and a fully modular methodology for the specification and the design of distributed systems and their components is obtained.

TL;DR: In this paper, the authors generalize some results known for dynamic algebras to test algesbras and show that every free algebra in the equational class generated by separable test algebra is isomorphic to a Kripke test structure.

TL;DR: It is found that composition of correct implementations is correct if terminating programs are implemented by terminating programs, and syntactical criteria to guarantee correctness of composition is provided.

TL;DR: The persistency criteria developed here mainly concern classes of parameter algebras with “built-in” logic.

TL;DR: It is proved that this subproblem in the generalized algorithm for the two-variable pattern-finding problem involves a sub-problem of finding common paths of pattern automata, which is NP-hard.

TL;DR: This paper argues that the algorithm presented is within some polynomial function of the optimal nondeterministic run time for many classes of these machines and shows that in most cases, the complexity of the nonemptiness problem does not change significantly when the reversal bound is dropped for one of the counters.

TL;DR: This paper examines the generating power of a simple extension of the well studied node-label controlled graph grammars, and shows that the extension, called handle NLC grammARS, gives the ability to generate any recursively enumerable graph language.

TL;DR: It is shown that both the standard and parametrized actualization are compatible with the previously introduced notion of submodule and with the union operation.

TL;DR: This theorem provides a solution to the Fliess conjecture in a restricted case and if the result could be extended to finite unions of the FP∗ above, the FlIess conjecture could be solved.