
Accession Number : ADA188620
Title : Characterizing Kripke Structures in Temporal Logic.
Descriptive Note : Interim rept.,
Corporate Author : CARNEGIEMELLON UNIV PITTSBURGH PA DEPT OF COMPUTER SCIENCE
Personal Author(s) : Browne, M C ; Clarke, E M ; Grumberg, O
PDF Url : ADA188620
Report Date : Dec 1987
Pagination or Media Count : 23
Abstract : The question of whether branchingtime temporal logic or lineartime temporal logic is best for reasoning about concurrent programs is one of the most controversial issues in logics of programs. Concurrent programs are usually modelled by labelled statetransition graphs in which some state is designated as the initial state. For historical reasons such graphs are called Kripke structures. In linear temporal logic operators are provided for describing events along a single time path (i.e., along a single path in a Kripke structure). In a branchingtime logic the temporal operators quantify over the futures that are possible from a given state (i.e., over the possible paths that lead from a state). It is well known that the two types of temporal logic have different expressive powers. Linear temporal logic, for example, can express certain fairness properties that cannot be expressed in branchingtime temporal logic. On the other hand, certain practical decision problems like model checking are easier for branchingtime temporal logic than for linear temporal logic. This paper provides further insight on which type of logic is best. It is shown that if two finite Kripke structures can be distinguished by some formula that contains both branchingtime and lineartime operators, then the structures can be distinguished by a formula that contains only branching time operators. Specifically, we show that if two finite Kripke structures can be distinguished by some formula of the logic CTL (i.e., if there is some CTL formula that is true in one but not in the other), then they can be distinguished by some formula of the logic CTL.
Descriptors : *COMPUTER LOGIC, *PARALLEL PROCESSING, DECISION MAKING, FORMULATIONS, PATHS, TIME, HIERARCHIES
Subject Categories : Computer Programming and Software
Distribution Statement : APPROVED FOR PUBLIC RELEASE