arXiv subjects

Edward Hermann Haeusler

Publications and source records attributed to Edward Hermann Haeusler.

23 records · Page 2Linked to original sources

arXiv2015

Propositional Logics Complexity and the Sub-Formula Property

In 1979 Richard Statman proved, using proof-theory, that the purely implicational fragment of Intuitionistic Logic (M-imply) is PSPACE-complete. He showed a polynomially bounded translation from full Intuitionistic Propositional Logic into its implicational fragment. By the PSPACE-completeness of S4, proved by Ladner, and the Goedel translation from S4 into Intuitionistic Logic, the PSPACE- completeness of M-imply is drawn. The sub-formula principle for a deductive system for a logic L states that whenever F1,...,Fk proves A, there is a proof in which each formula occurrence is either a sub-formula of A or of some of Fi. In this work we extend Statman result and show that any propositional (possibly modal) structural logic satisfying a particular formulation of the sub-formula principle is in PSPACE. If the logic includes the minimal purely implicational logic then it is PSPACE-complete. As a consequence, EXPTIME-complete propositional logics, such as PDL and the common-knowledge epistemic logic with at least 2 agents satisfy this particular sub-formula principle, if and only if, PSPACE=EXPTIME. We also show how our technique can be used to prove that any finitely many-valued logic has the set of its tautologies in PSPACE.

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arXiv2014

How many times do we need and assumption ?

In this article we present a class of formulas Fn, n in Nat, that need at least 2^n assumptions to be proved in a normal proof in Natural Deduction for purely implicational minimal propositional logic. In purely implicational classical propositional logic, with Peirce's rule, each Fn is proved with only one assumption in Natural Deduction in a normal proof. Hence, the formulas Fn have exponentially sized proofs in cut-free Sequent Calculus and Tableaux. In fact 2^n is the lower-bound for normal proofs in ND, cut-free Sequent proofs and Tableaux. We discuss the consequences of the existence of this class of formulas for designing automatic proof-procedures based on these deductive systems.

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arXiv2014

Reasoning about Games via a First-order Modal Model Checking Approach

In this work, we present a logic based on first-order CTL, namely Game Analysis Logic (GAL), in order to reason about games. We relate models and solution concepts of Game Theory as models and formulas of GAL, respectively. Precisely, we express extensive games with perfect in- formation as models of GAL, and Nash equilibrium and subgame perfect equilibrium by means of formulas of GAL. From a practical point of view, we provide a GAL model checker in order to analyze games automatically. We use our model checker in at least two directions: to find solution con- cepts of Game Theory; and, to analyze players that are based on standard algorithms of the AI community, such as the minimax procedure.

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arXiv2014

Proof-graphs for Minimal Implicational Logic

It is well-known that the size of propositional classical proofs can be huge. Proof theoretical studies discovered exponential gaps between normal or cut free proofs and their respective non-normal proofs. The aim of this work is to study how to reduce the weight of propositional deductions. We present the formalism of proof-graphs for purely implicational logic, which are graphs of a specific shape that are intended to capture the logical structure of a deduction. The advantage of this formalism is that formulas can be shared in the reduced proof. In the present paper we give a precise definition of proof-graphs for the minimal implicational logic, together with a normalization procedure for these proof-graphs. In contrast to standard tree-like formalisms, our normalization does not increase the number of nodes, when applied to the corresponding minimal proof-graph representations.

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arXiv2014

An Intuitionisticaly based Description Logic

This article presents iALC, an intuitionistic version of the classical description logic ALC, based on the framework for constructive modal logics presented by Simpson \cite{simpson95} and related to description languages, via hybrid logics, by dePaiva \cite{depaiva2003}. This article correcta and extends the presentation of iALC appearing in \cite{PHR:2010}. It points out the difference between iALC and the intuitionistic hybrid logic presented in \cite{depaiva2003}. Completeness and soundness proofs are provided. A brief discussion on the computacional complexity of iALC provability is taken. It is worth mentioning that iALC is used to formalize legal knowledge \cite{HPR:2010a,HPR:2010ab,Jurix, HPR:2011}, and in fact, was specifically designed to this goal.

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