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Journal of Philosophical Logic
Article . 1996 . Peer-reviewed
License: Springer TDM
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image/svg+xml Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao Closed Access logo, derived from PLoS Open Access logo. This version with transparent background. http://commons.wikimedia.org/wiki/File:Closed_Access_logo_transparent.svg Jakob Voss, based on art designer at PLoS, modified by Wikipedia users Nina and Beao
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Valuational semantics of rule derivability

Authors: Lloyd Humberstone;

Valuational semantics of rule derivability

Abstract

Syntactic Concepts. We work with an arbitrary but fixed sentential language \(L\), for which sequents are pairs \(\langle\Gamma,A \rangle\) with \(\Gamma \subseteq L\), \(A\in L\). An \(n\)-premiss rule \(\rho\) is an \((n+1)\)-ary relation on the set of sequents. If \(\langle \sigma_0, \dots, \sigma_n \rangle\in\rho\) then \(\sigma_n\) is the conclusion-sequent and \(\sigma_0, \dots, \sigma_{n-1}\) the premiss-sequents for the application \(\langle \sigma_0, \dots, \sigma_n \rangle\) of \(\rho\). A rule \(\rho\) is derivable from a set of rules \(R\) if every set of sequents closed under each rule in \(R\) is closed under \(\rho\). Structural rules are understood in the sense of Gentzen: as rules whose applications consist of all instantiations of a sequent-to-sequent schema in which no connective of \(L\) appears (by contrast with operational rules). Closure under certain structural rules is necessary and sufficient for a set of sequents to constitute a consequence relation; these are the rules \((\mathbb{R})=\) the zero-premiss rule \(\{ \langle \{A\}, A\rangle \mid A\in L\}\), \((\mathbb{M}) =\) the one-premiss rule \(\{\langle \langle \Gamma, A\rangle, \langle \Delta,A \rangle\rangle \mid \Gamma \subseteq \Delta \subseteq L\}\), and the cut or transitivity rule \((\mathbb{T})\) which we will further specify here. Let \(S= \{(\mathbb{R}), (\mathbb{M}), (\mathbb{T})\}\). Semantic Concepts. A valuation (for \(L)\) is a mapping from the set of formulas (of \(L)\) to the two element set \(\{T,F\}\) of truth-values. A sequent \(\sigma= \langle \Gamma,A \rangle\) holds on a valuation \(v\) if \(v(C)=T\) for all \(C\in\Gamma\) implies \(v(A)= T\). For a class \(V\) of valuations, we say sequent \(\sigma\) is \(V\)-valid if \(\sigma\) holds on each \(v\in V\). The local range, \(\text{Loc} (R)\), of a collection of rules \(R\) is the set of all valuations \(v\) such that for any \(\langle \sigma_0, \dots, \sigma_n \rangle\in\rho \in R\) if each of \(\sigma_0, \dots, \sigma_{n-1}\) holds on \(v\), then \(\sigma_n\) holds on \(v\). The global range, \(\text{Glo} (R)\), of a collection \(R\) of rules is the class of sets \(V\) of valuations such that for any \(\langle \sigma_0, \dots, \sigma_n \rangle \in\rho \in R\) if each of \(\sigma_0, \dots, \sigma_{n-1}\) is \(V\)-valid then \(\sigma_n\) is \(V\)-valid. The local and global consequence operations \(LCn\) and \(GCn\) are closure operations defined on the set of rules by: \[ LCn (R) = \biggl\{\rho \mid \text{Loc} (R) \subseteq \text{Loc} \bigl(\{\rho\} \bigr) \biggr\}, \quad GCn (R) = \biggl\{\rho\mid \text{Glo} (R) \subseteq \text{Glo} \bigl(\{\rho\} \bigr) \biggr\}. \] Connections. The main connection between the above syntactic and semantic concepts is given by: \(\rho\in GCn(R)\) if and only if \(\rho\) is derivable from \(R \cup S\). By contrast, the local consequences of a set of rules \(R\) are not guaranteed to be derivable from \(R\) with assistance of the structural rules \(S\). (Examples are given.) Reference. The role of the `global' concepts here is a vindication of the emphasis placed on them in a related context by \textit{J. W. Garson} [``Categorical semantics'', in: J. M. Dunn and A. Gupta (eds.), Truth or consequences: Essays in honor of Nuel Belnap, 155-175, Kluwer, Dordrecht (1990)].

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Keywords

Abstract deductive systems, rules, consequence relation, closure operations, valuation

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
24
Top 10%
Top 10%
Average
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