A fully abstract game semantics of local exceptions

A fully abstract game semantics for an extension of Idealized Algol with locally declared exceptions is presented. It is based on "Hyland-Ong games" (J.M.E. Hyland & C.-H.L. Ong, 1995), but as well as relaxing the constraints which impose functional behavior (as in games models of other computational effects, such as continuations and references), new structure is added to plays in the form of additional pointers which track the flow of control. The semantics is proved to be fully abstract by a factorization of strategies into a "new-exception generator" and a strategy with local control flow. It is shown, using examples, that there is no model of exceptions which is a conservative extension of the semantics of Idealized Algol without the new pointers.