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1

Characterising Strongly Normalising Intuitionistic Terms

Santo J. E., Ivetić J., Likavec S.

Fundamenta Informaticae

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2012

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Vol. 121, nr 1/4

83-120

EN

This paper gives a characterisation, via intersection types, of the strongly normalising proof-terms of an intuitionistic sequent calculus (where LJ easily embeds). The soundness of the typing system is reduced to that of a well known typing system with intersection types for the ordinary λ-calculus. The completeness of the typing system is obtained from subject expansion at root position. Next we use our result to analyze the characterisation of strong normalisability for three classes of intuitionistic terms: ordinary λ-terms, ΛJ-terms (λ-terms with generalised application), and λx-terms (λ-terms with explicit substitution). We explain via our system why the type systems in the natural deduction format for ΛJ and λx known from the literature contain extra, exceptional rules for typing generalised application or substitution; and we show a new characterisation of the β-strongly normalising l-terms, as a corollary to a PSN-result, relating the λ-calculus and the intuitionistic sequent calculus. Finally, we obtain variants of our characterisation by restricting the set of assignable types to sub-classes of intersection types, notably strict types. In addition, the known characterisation of the b-strongly normalising l-terms in terms of assignment of strict types follows as an easy corollary of our results.

2

Arithmetical Proofs of Strong Normalization Results for Symmetric [lambda]-calculi

David R., Nour K.

Fundamenta Informaticae

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2007

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Vol. 77, nr 4

489-510

EN

We give arithmetical proofs of the strong normalization of two symmetric l-calculi corresponding to classical logic. The first one is the [`(l)]m[(m~)]-calculus introduced by Curien & Herbelin. It is derived via the Curry-Howard correspondence from Gentzen's classical sequent calculus LK in order to have a symmetry on one side between "program" and "context" and on other side between "call-by-name" and "call-by-value". The second one is the symmetric lm-calculus. It is the lm-calculus introduced by Parigot in which the reduction rule m?, which is the symmetric of m, is added. These results were already known but the previous proofs use candidates of reducibility where the interpretation of a type is defined as the fix point of some increasing operator and thus, are highly non arithmetical.

3

Logics for Real Time: Decidability and Complexity

Hirshfeld Y., Rabinovich A.

Fundamenta Informaticae

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2004

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Vol. 62, nr 1

1--28

EN

Over the last fifteen years formalisms for reasoning about metric properties of computations were suggested and discussed. First as extensions of temporal logic, ignoring the framework of classical predicate logic, and then, with the authors' work, within the framework of monadic logic of order. Here we survey our work on metric logic comparing it to the previous work in the field. We define a quantitative temporal logic that is based on a simple modality within the framework of monadic predicate Logic. Its canonical model is the real line (and not an w-sequence of some type). It can be interpreted either by behaviors with finite variability or by unrestricted behaviors. For finite variability models it is as expressive as any logic suggested in the literature. For unrestricted behaviors our treatment is new. In both cases we prove decidability and complexity bounds using general theorems from logic (and not from automata theory).

4

Strong normalisation of cut-elimination in clasical logic

Urban C., Bierman G.M.

Fundamenta Informaticae

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2001

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Vol. 45, nr 1,2

123-155

EN

In this paper we present a strongly normalising cut-elimination procedure for classical logic. This procedure adapts Gentzen's standard cut-reductions, but is less restrictive than previous strongly normalising cut-elimination procedures. In comparison, for example, with works by Dragalin and Danos et al., our procedure requires no special annotations on formulae and allows cut-rules to pass over other cut-rules. In order to adapt the notion of symmetric reducibility candidates for proving the strong normalisation property, we introduce a novel term assignment for sequent proofs of classical logic and formalise cut-reductions as term rewriting rules.