Andrew Pitts
University of Cambridge Computer Laboratory

Equivariant Semantics


Many kinds of names (or identifiers) occurring in programming languages and logical calculi are "atomic", in the sense that the structure of a name is immaterial: all that matters are distinctions between names and the association of names to the things named. The main point of this talk is to emphasize the usefulness of taking into account the "equivariance property" of semantics---namely that meaning is invariant under permuting such names. We give a gentle introduction to "nominal sets", a mathematical framework with names as atoms, which makes equivariance ubiquitous and can express the crucial property of "freshness" of names in a syntax-independent way. There are simple constructions on nominal sets for functions, for name-abstraction and for name-restriction that illuminate the relationship between these notions and that of dynamic allocation of names in operational semantics.

Host:  Frank Pfenning
Appointments:  Jennifer Landefeld

Principles of Programming Seminars

Monday, June 28, 2004
3:30 p.m.
Wean Hall 4623