Showing papers in "Theoretical Computer Science in 1982"

TL;DR: Methods of proving that a term-rewriting system terminates are presented, based on the notion of "simplification orderings", orderings in which any term that is homeomorphically embeddable in another is smaller than the other.

TL;DR: The oracle Turing machine is introduced as the formal model for computing real functions and the class of polynomial time computable real functions is defined, and several characterizations of this class will be given.

TL;DR: It is proved, that differentiating according to the functional level of recursion leads to two infinite hierarchies of recursive languages, the IO - and OI-hierarchies, which can be characterized as canonical extensions of the regular, context-free, and IO-and-macro languages, respectively.

TL;DR: A sequential denotational semantics for sequential programming languages is provided, based on a new notion of sequential algorithm on the Kahn-Plotkin concrete data structures, which form a cartesian closed category with straightforward solutions to recursive domain equations.

TL;DR: A theory of formal power series on trees is proposed, some of their basic properties are presented, and various examples of applications are presented which, it is hoped, will show the interest of its development within the framework sketched.

TL;DR: Certain natural problems are shown to be complete for symmetric space complexity classes, and the relationship of symmetry to determinism and nondeterminism is investigated.

TL;DR: It is shown that an attribute system can be translated (in a certain way) into a recursive program scheme if and only if it is strongly noncircular, which is decidable in polynomial time.

TL;DR: The main results of the paper are different kinds of correctness criteria which are applied to a number of illustrating examples including the implementation of sets by hash-tables.

TL;DR: It is argued that the transformational approach is more fundamental, for it allows to describe mixed computation in all its variety and moreover, to relate mixed computation to other kinds of program manipulation: execution, optimization, macroprocessing, synthesis.

TL;DR: It is shown that the class of all sets which are both P-selective and have positive reductions to their complements is P, and it follows that various naturally defined apparently intractible problems are not p- selective unless P = NP.

TL;DR: It is shown that the problem is log space complete for deterministic polynomial time, so the maximum flow problem probably has no algorithm which needs only O(logk n) storage space for any constant k.

TL;DR: The syntactic structure of sets of ancestors and sets of descendants is considered, as well as that of unions of congruence classes, taken over (infinite) context-free languages or regular sets.

TL;DR: An approximation algorithm similar to Christofides' algorithm for the traveling salesman problem is shown to possess the same worst-case bound of 3 2 when applied to the biconnectivity augmentation problem.

TL;DR: The main conclusion is that the reachability types and therefore the system properties, can be characterized by simple relations involving the set of the possible initial states and fixed points of certain continuous predicate trasformers depending on theSet of target states.

TL;DR: It is shown that several reducibilities in this class differ over the recursive sets and assuming NP ≠ coNP, that they each determine different classes of NP-hard sets.

TL;DR: An O (¦A¦ log 2 ¦V¦) algorithm to partition a graph, where V is the set of vertices and A theSet of arcs, is presented, extending Hopcroft's fast partitioning algorithm.

TL;DR: The following theorem is proved: “A semigroup morphism defined on a three letter alphabet is squarefree iff the images of the squarefree words of length 5 are squarefree”.

TL;DR: This paper considers a possible classification of embedding mechanisms for (node-rewriting) graph grammars, which allows one to fit a number of existing notions of a graph grammar into a common framework and points out new “natural” possibilities for defining the embedding mechanism in a graph Grammar.

TL;DR: A uniform method for constructing sets which diagonalize over certain complexity classes while preserving other complexity properties is given, obtaining some known results as well as some new ones as corollaries of the main theorem.

TL;DR: A time-optimal solution to the firing-squad-synchronization-problem of n-dimensional rectangles with the general at an arbitrary position is presented and the straightforward generalization to larger n is outlined.

TL;DR: This article studies some problems as: how to realize the inverse transformation of homomorphism?

TL;DR: It is shown that color-families are dense, in the sense that between any two families one can `squeeze in?

TL;DR: Some basic automaton-theoretic conditions on relational structures are presented which give preservation theorems for decidability under certain direct products.

TL;DR: In this paper, the subgraph isomorphism problem for outerplanar graphs is shown to be NP-hard. But the problem remains NP-complete even when the strongest connectivity requirements are imposed on both graphs.

TL;DR: The proof method I--.~ is proved to be strictly stronger than Floyd’s method in Section 6 and different semantics ?

TL;DR: Two different definitions of inclusion and a definition of equivalence between schemata are given and necessary and sufficient conditions for inclusion and equivalence are proved for two classes ofschemata, meaningful in the relational theory.

TL;DR: It is shown how the method of Fischer and Rabin can be extended to get good lower bounds for Presburger arithmetic with a bounded number of quantifier alternations.

TL;DR: Since L is accepted by a two-way deterministic pushdown automation, it is shown that one pushdown stack is more powerful than one counter for deterministic two way machines.

TL;DR: This paper investigates infinite words, and sets of them, associated with DOL and DTOL systems and main emphasis is on characterization and decidability results.