An inductive abstract semantics for coFJ

Abstract

We describe an inductive abstract semantics for coFJ, a Java-like calculus where, when the same method call is encountered twice, non-termination is avoided, and the programmer can decide the behaviour in this case, by writing a codefinition. The proposed semantics is abstract in the sense that evaluation is non-deterministic, and objects are possibly infinite. However, differently from typical coinductive handling of infinite values, the semantics is inductive, since it relies on detection of cyclic calls. Whereas soundness with respect to the reference coinductive semantics has already been proved, we conjecture that completeness with respect to the regular subset of such semantics holds as well. This relies on the fact that in the proposed semantics detection of cycles is non-deterministic, that is, does not necessarily happens the first time a cycle is found.