A number of similar decidable word problems from automata theory and logic whose inherent computational complexity can be precisely characterized in terms of time or space requirements on deterministic or nondeterministic Turing machines are considered.Expand

This work forms a general notion of Structured Operational Semantics for processes with Guarded recursion (GSOS), and demonstrates that bisimulation does not agree with trace congruence with respect to any set of GSOS-definable contexts.Expand

This seems simple enough, but let’s play with this definition. The Pythagoreans, an ancient sect of mathematical mystics, said that a number is perfect if it equals the sum of its positive integral… Expand

Abstract Any decision procedure for the word problems for commutative semigroups and polynomial deals inherently requires computational storage space growing exponentially with the size of the… Expand

The structure of the functions computable in time or space bounded by t is investigated for recursive functions t. The t-computable classes are shown to be closed under increasing recursively… Expand

The languages recognizable by time- and space-restricted multiple-counter machines are compared to the languages recognizable by similarly restricted multipletape Turing machines. Special emphasis is… Expand

Improved models and stronger proof rules are developed to handle examples of the Store Model of Halpern-Meyer-Trakhtenbrot for a limited fragment of ALGOL in which procedures do not take procedure parameters.Expand

An elementary, purely algebraic definition of model for the untyped lambda calculus is given, shown to be equivalent to the natural semantic definition based on environments, which yields a completeness theorem for, the standard axioms for lambda convertibility.Expand