Characterising strongly normalising intuitionistic sequent terms

  • Authors:
  • J. Espírito Santo;S. Ghilezan;J. Ivetić

  • Affiliations:
  • Mathematics Department, University of Minho, Portugal;Faculty of Engineering, University of Novi Sad, Serbia;Faculty of Engineering, University of Novi Sad, Serbia

  • Venue:
  • TYPES'07 Proceedings of the 2007 international conference on Types for proofs and programs
  • Year:
  • 2007

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Abstract

This paper gives a characterisation, via intersection types, of the strongly normalising 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. This paper's sequent term calculus integrates smoothly the λ-terms with generalised application or explicit substitution. Strong normalisability of these terms as sequent terms characterises their typeability in certain "natural" typing systems with intersection types. The latter are in the natural deduction format, like systems previously studied by Matthes and Lengrand et al., except that they do not contain any extra, exceptional rules for typing generalised applications or substitution.