Action Semantics is a framework for the formal description of programming languages. Its main advantage over other frameworks is pragmatic: action-semantic descriptions (ASDs) scale up smoothly to realistic programming languages. This is due to the inherent extensibility and modifiability of ASDs, ensuring that extensions and changes to the described language require only proportionate changes in its description.

Action Semantics is a formal method of defining programming language semantics in which actions describe the manipulation of three entities: transients, bindings, and the store. Due to the high-level nature of Action Semantics, actions cannot be directly translated into efficient code in an Action Semantics-based compiler. However, by applying sort inference to an action, it is possible to transform it to a lowlevel action that can be translated into efficient code. This paper briefly introduces Action Semantics. The problem of Action Semantics-directed compilation is then demonstrated through an example. Finally, sort inference is applied to an action and it is subsequently transformed to an action more suitable for compilation.