**Organisers**: S Abramsky (*Imperial College, London*), G Kahn (*INRIA, Sophia-Antipolis*), J C Mitchell (*Stanford*), A M Pitts (*Cambridge*)

### Semantics of Computation Seminar

Friday September 1, 2:15 pm

#### Domains, Functor Categories and the Pi-Calculus

Ian Stark

University of Cambridge and University of Pisa

This talk describes a domain model for the pi-calculus, building on Abramsky's domain equation for bisimulation and Ingrlfsdrttir's model of value-passing CCS. The main innovation is to work within a functor category, over a base of ordinary cpo's. This gives additional indexing structure that allows us to talk about names, freshness, visibility and non-interference through abstract categorical constructions. The resulting model gives a strong, late semantics, and can express various relations between processes: bisimulation, equivalence, and D-equivalence for any distinction D.