scholarly journals Hypersequent calculi for non-normal modal and deontic logics: countermodels and optimal complexity

2020 ◽  
Author(s):  
Tiziano Dalmonte ◽  
Björn Lellmann ◽  
Nicola Olivetti ◽  
Elaine Pimentel
Keyword(s):  
Search Strategy ◽  
Cut Elimination ◽  
Relational Semantics ◽  
Optimal Complexity ◽  
Proof Search ◽  
Polynomial Size ◽  
Hypersequent Calculi

Abstract We present some hypersequent calculi for all systems of the classical cube and their extensions with axioms ${T}$, ${P}$ and ${D}$ and for every $n \geq 1$, rule ${RD}_n^+$. The calculi are internal as they only employ the language of the logic, plus additional structural connectives. We show that the calculi are complete with respect to the corresponding axiomatization by a syntactic proof of cut elimination. Then, we define a terminating proof search strategy in the hypersequent calculi and show that it is optimal for coNP-complete logics. Moreover, we show that from every failed proof of a formula or hypersequent it is possible to directly extract a countermodel of it in the bi-neighbourhood semantics of polynomial size for coNP logics, and for regular logics also in the relational semantics. We finish the paper by giving a translation between hypersequent rule applications and derivations in a labelled system for the classical cube.

Relational semantics and a relational proof system for full Lambek calculus

1998 ◽  
Vol 63 (2) ◽  
pp. 623-637 ◽  
Author(s):  
Wendy MacCaull
Keyword(s):  
Proof Theory ◽  
Kripke Semantics ◽  
Substructural Logic ◽  
Lambek Calculus ◽  
Relational Semantics ◽  
Complete Proof ◽  
Proof Search ◽  
Proof Tree ◽  
Relational Logic ◽  
Completeness Theorems

AbstractIn this paper we give relational semantics and an accompanying relational proof theory for full Lambek calculus (a sequent calculus which we denote by FL). We start with the Kripke semantics for FL as discussed in [11] and develop a second Kripke-style semantics, RelKripke semantics, as a bridge to relational semantics. The RelKripke semantics consists of a set with two distinguished elements, two ternary relations and a list of conditions on the relations. It is accompanied by a Kripke-style valuation system analogous to that in [11]. Soundness and completeness theorems with respect to FL hold for RelKripke models. Then, in the spirit of the work of Orlowska [14], [15], and Buszkowski and Orlowska [3], we develop relational logic RFL. The adjective relational is used to emphasize the fact that RFL has a semantics wherein formulas are interpreted as relations. We prove that a sequent Γ → α in FL is provable if and only if a translation, t(γ1 ● … ● γn ⊃ α)ευu, has a cut-complete fundamental proof tree. This result is constructive: that is, if a cut-complete proof tree for t(γ1 ● … ● γn ⊃ α)ευu is not fundamental, we can use the failed proof search to build a relational countermodel for t(γ1 ● … ● γn ⊃ α)ευu and from this, build a RelKripke countermodel for γ1 ● … ● γn ⊃ α. These results allow us to add FL, the basic substructural logic, to the list of those logics of importance in computer science with a relational proof theory.

Cut elimination and complexity bounds for intuitionistic epistemic logic

2020 ◽  
Vol 30 (1) ◽  
pp. 281-294
Author(s):  
Vladimir N Krupski
Keyword(s):  
Epistemic Logic ◽  
Sequent Calculus ◽  
Formal System ◽  
Point Of View ◽  
Cut Elimination ◽  
Polynomial Space ◽  
Complexity Bounds ◽  
Proof Search

Abstract The formal system of intuitionistic epistemic logic (IEL) was proposed by S. Artemov and T. Protopopescu. It provides the formal foundation for the study of knowledge from an intuitionistic point of view based on Brouwer–Heyting–Kolmogorov semantics of intuitionism. We construct a cut-free sequent calculus for IEL and establish that polynomial space is sufficient for the proof search in it. We prove that IEL is PSPACE-complete.

scholarly journals Bunched Hypersequent Calculi for Distributive Substructural Logics

10.29007/ngp3 ◽  
2018 ◽  
Author(s):  
Agata Ciabattoni ◽  
Revantha Ramanayake
Keyword(s):  
Large Class ◽  
General Rule ◽  
Expressive Power ◽  
Substructural Logics ◽  
Cut Elimination ◽  
Lambek Calculus ◽  
Hypersequent Calculi

We introduce a new proof-theoretic framework which enhances the expressive power of bunched sequents by extending them with a hypersequent structure. A general cut-elimination theorem that applies to bunched hypersequent calculi satisfying general rule conditions is then proved. We adapt the methods of transforming axioms into rules to provide cutfree bunched hypersequent calculi for a large class of logics extending the distributive commutative Full Lambek calculus DFLe and Bunched Implication logic BI. The methodology is then used to formulate new logics equipped with a cutfree calculus in the vicinity of Boolean BI.

scholarly journals Cut Elimination Theorem for Non-Commutative Hypersequent Calculus

2017 ◽  
Vol 46 (1/2) ◽  
Author(s):  
Andrzej Indrzejczak
Keyword(s):  
Temporal Logic ◽  
Cut Elimination ◽  
Temporal Logics ◽  
Hypersequent Calculi ◽  
Flow Of Time

Hypersequent calculi (HC) can formalize various non-classical logics. In [9] we presented a non-commutative variant of HC for the weakest temporal logic of linear frames Kt4.3 and some its extensions for dense and serial flow of time. The system was proved to be cut-free HC formalization of respective temporal logics by means of Schütte/Hintikka-style semantical argument using models built from saturated hypersequents. In this paper we present a variant of this calculus for Kt4.3 with a constructive syntactical proof of cut elimination.

A multi-labelled sequent calculus for Topo-Logic

2020 ◽  
Vol 30 (2) ◽  
pp. 663-696
Author(s):  
Ian Shillito
Keyword(s):  
Structural Properties ◽  
Epistemic Logic ◽  
Search Strategy ◽  
Sequent Calculus ◽  
Search Tree ◽  
Topological Spaces ◽  
Label Technique ◽  
Proof Search ◽  
Labelled Sequent Calculus

Abstract We present a labelled sequent calculus for a trimodal epistemic logic exhibitied in Baltag et al. (2017, Logic, Rationality, and Interaction, pp. 330–346), an extension of the so called ‘Topo-Logic’. To the best of our knowledge, our calculus is the first proof-calculus for this logic. This calculus is obtained via an adaptation of the label technique by internalizing a semantics over topological spaces. This internalization leads to the generation of two kinds of labels in our calculus and the labelling of formulae by pairs of labels. These novelties give tools to provide a simple calculus that is intuitively connected to the semantics. We prove that this calculus enjoys many structural properties such as admissibility of cut, admissibility of contraction and invertibility of its rules. Finally, we exhibit a proof search strategy for our calculus that allows us to prove completeness in a direct way by the extraction of a countermodel from a failure of proof. To define this strategy, we design a tool for controlling the generation of labels in the construction of a search tree, although the termination of this strategy is still open.

Cut-Elimination for Provability Logic by Terminating Proof-Search: Formalised and Deconstructed Using Coq

2021 ◽  
pp. 299-313
Author(s):  
Rajeev Goré ◽  
Revantha Ramanayake ◽  
Ian Shillito
Keyword(s):  
Cut Elimination ◽  
Provability Logic ◽  
Proof Search

scholarly journals Proofs, denotational semantics and observational equivalences in Multiplicative Linear Logic

2007 ◽  
Vol 17 (2) ◽  
pp. 341-359 ◽  
Author(s):  
MICHELE PAGANI
Keyword(s):  
Linear Logic ◽  
Denotational Semantics ◽  
Cut Elimination ◽  
Relational Semantics ◽  
Observational Equivalence ◽  
Proof Nets ◽  
General Method

We study full completeness and syntactical separability of MLL proof nets with the mix rule. The general method we use consists of first addressing these two questions in the less restrictive framework of proof structures, and then adapting the results to proof nets.At the level of proof structures, we find a semantical characterisation of their interpretations in relational semantics, and define an observational equivalence that is proved to be the equivalence induced by cut elimination. Hence, we obtain a semantical characterisation (in coherent spaces) and an observational equivalence for the proof nets with the mix rule.

scholarly journals S5-Style Non-Standard Modalities in a Hypersequent Framework

2021 ◽  
pp. 1-30
Author(s):  
Yaroslav Petrukhin
Keyword(s):  
Cut Elimination ◽  
Hypersequent Calculi ◽  
Soundness And Completeness ◽  
Completeness Theorems

The aim of the paper is to present some non-standard modalities (such as non-contingency, contingency, essence and accident) based on S5-models in a framework of cut-free hypersequent calculi. We also study negated modalities, i.e. negated necessity and negated possibility, which produce paraconsistent and paracomplete negations respectively. As a basis for our calculi, we use Restall's cut-free hypersequent calculus for S5. We modify its rules for the above-mentioned modalities and prove strong soundness and completeness theorems by a Hintikka-style argument. As a consequence, we obtain a cut admissibility theorem. Finally, we present a constructive syntactic proof of cut elimination theorem.

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