During Peter’s DPhil studies, supervised by Christopher Strachey, he developed a prototype of a system for executing programs based on their denotational semantics.
It involved partial evaluation of lambda-notation, implemented using Wadsworth's call-by-need algorithm. He continued the development of the system as a postdoc at Oxford, and subsequently at Aarhus, Denmark. The system was called SIS: Semantics Implementation System.
In this talk, Peter recalls Strachey's influence on his research and on the development of SIS, starting from Strachey’s summer school course on symbolic computation at the PRG in 1969.