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We describe a mu-calculus which amounts to modal logic plus a minimization operator, and show that its satisfiability problem is decidable in exponential time. This result subsumes corresponding results for propositional dynamic logic with test and converse, thus supplying a better setting for those results. It also encompasses similar results for a logic of flowgraphs. This work provides an intimate...
We briefly survey the major proposals for models of programs and show that they all lead to the same propositional theory of programs. Methods of algebraic logic dominate in the proofs. One of the connections made between the models, that involving language models, is quite counterintuitive. The common theory has already been shown to be complete in deterministic exponential time; we give here a simpler...
Decision procedures for validity in intuitionistic propositional calculus and modal propositional calculus are given which require a running time proportional to a polynomial in the length of the formula on a nondeterministic Turing machine. Using a theorem of Cook's and well-known transformations from intuitionistic to classical and modal to intuitionistic logics, the validity problem for intuitionistic...
Let Σ be a finite alphabet, Σ* the free monoid generated by Σ and |x| the length of x ε Σ*. For any integer k ≥ 0, fk(x)(tk (x)) is x if |x| ≪ k+1, and it is the prefix (suffix) of x of length k, otherwise. Also let mk+1 (x) = {v|x = uvw and |v| = k+1}. For x,y ε Σ* define x ∼k+1y iff fk(x) = fk(y), tk(x) = tk(y) and mk+1(x) = mk+1 (y). The relation ∼k+1 is a congruence of finite index over Σ*. An...
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