traction Problem for PCF Hyland-Ong games model Concrete Representation Compositional Semantics? A Concrete Representation of Observational Equivalence for PCF Martin Churchill, Jim Laird and Guy McCusker University of Bath March 28th, 2009 GaLoP workshop, University of York Martin Churchill, Jim Laird and Guy McCusker University of BathA Concrete Representation of Observational Equivalence for PC