Types and Related Systems
were introduced near the end of the 1970s to overcome the limitations
of Curry's type assignment system and to provide a characterization of
the strongly normalizing terms of the Lambda Calculus. The key idea is
to introduce an intersection type constructor /\ such that a term of
type t/\s can be used at both type t and s within the same context.
This provides a finite polymorphism where various, even unrelated,
types of the term are listed explicitly, differently from the more
widely used universally quantified types where the polymorphic type is
common schema which stands for its various type instances. As a
consequence, more terms (all and only the normalizing terms) can be
typed than with universal polymorphism.
Intersection types have been one of the first examples of behavioural type theory: they provide an abstract specification of computational properties, by expressing a finer and more precise input/output relation than standard, commonly used, type systems can do.
Although intersection types were initially intended for use in analysing and/or synthesizing lambda models as well as in analysing normalization properties, over the last twenty years the scope of the research on intersection types and related systems has broadened in many directions. Restricted (and more manageable) forms have been investigated, such as refinement types. Type systems based on intersection type theory have been extensively studied for practical purposes, such as program analysis. The dual notion of union types turned out to be quite useful for programming languages. Finally, the behavioural approach to types, which can give a static specification of computational properties, has become central in the most recent research on type theory.
The ITRS 2012 workshop aims to bring together researchers working on both the theory and practical applications of systems based on intersection types and related approaches (e.g., union types, refinement types, behavioural types, recursive types, etc...).
Permanent Home Page of ITRS: http://www.macs.hw.ac.uk/~jbw/itrs/
Mariangiola Dezani-Ciancaglini (Università di Torino, Italy)
Joe Wells Chair (Heriot-Watt University, Edinburgh, Scotland).