Compositional characterisations of λ-terms using intersection types

  • Authors:

  • M. Dezani-Ciancaglini;F. Honsell;Y. Motohama

  • Affiliations:

  • Dipartimento di Informatica, Universitá di Torino, Torino, Italy;Dipartimento di Mathematica ed Informatica, Universitá di Udine, Udine, Italy;Dipartimento di Mathematica ed Informatica, Universitá di Udine, Udine, Italy

  • Venue:
  • Theoretical Computer Science - Mathematical foundations of computer science 2000
  • Year:
  • 2005

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Abstract

We show how to characterise compositionally a number of evaluation properties of λ-terms using Intersection Type assignment systems. In particular, we focus on termination properties, such as strong normalisation, normalisation, head normalisation, and weak head normalisation. We consider also the persistent versions of such notions. By way of example, we consider also another evaluation property, unrelated to termination, namely reducibility to a closed term.Many of these characterisation results are new, to our knowledge, or else they streamline, strengthen, or generalise earlier results in the literature.The completeness parts of the characterisations are proved uniformly for all the properties, using a set-theoretical semantics of intersection types over suitable kinds of stable sets. This technique generalises Krivine's and Mitchell's methods for strong normalisation to other evaluation properties.