We proved recently that the extensional collapse of the relational model of linear logic coincides with its Scott model, whose objects are preorders and morphisms are downwards closed relations. This result is obtained by the construction of a new model whose objects can be understood as preorders equipped with a realizability predicate. We present this model, which features a new duality, and explain how to use it for reducing normalization results in idempotent intersection types (usually proved by reducibility) to purely combinatorial methods. We illustrate this approach in the case of the call-by-value lambda-calculus, for which we introduce a new resource calculus, but it can be applied in the same way to many different calculi.

Collapsing non-idempotent intersection types

The resource calculus is an extension of the λ-calculus allowing to model resource consumption. Namely, the argument of a function comes as a finite multiset of resources, which in turn can be either linear or reusable, giving rise to non-deterministic choices, expressed by a formal sum. Using the λ-calculus terminology, we call solvable a term that can interact with the environment: solvable terms represent meaningful programs. Because of the non-determinism, different definitions of solvability are possible in the resource calculus. Here we study the optimistic (angelical, or may) notion, and so we define a term solvable whenever there is a simple head context reducing the term into a sum where at least one addend is the identity. We give a syntactical, operational and logical characterization of this kind of solvability.

/pdf/solvability-in-resource-lambda-calculus-12bnfr57eo.pdf

Solvability in resource lambda-calculus

We study the notion of solvability in the resource calculus, an extension of the λ-calculus modelling resource consumption. Since this calculus is non-deterministic, two different notions of solvability arise, one optimistic (angelical, may) and one pessimistic (demoniac, must). We give a syntactical, operational and logical characterization for the may-solvability and only a partial characterization of the must-solvability. Finally, we discuss the open problem of a complete characterization of the must-solvability.

/pdf/linearity-non-determinism-and-solvability-kclnfh3k96.pdf

Linearity, Non-determinism and Solvability

https://hal.archives-ouvertes.fr/hal-01244842/document

Proof nets and the call-by-value λ-calculus

We study the resource calculus --- the non-lazy version of Boudol's *** -calculus with resources. In such a calculus arguments may be finitely available and mixed, giving rise to nondeterminism, modelled by a formal sum. We define parallel reduction in resource calculus and we apply, in such a nondeterministic setting, the technique by Tait and Martin-Lof to achieve confluence. Then, slightly generalizing a technique by Takahashi, we obtain a standardization result.

/pdf/parallel-reduction-in-resource-lambda-calculus-3gcwpssnjj.pdf

Parallel Reduction in Resource Lambda-Calculus

http://www.cs.unibo.it/~tranquil/content/docs/intudiffnet.pdf

Paolo Tranquilli

Papers

Intuitionistic differential nets and lambda-calculus