Action Semantics for an Executable UML

UML currently lacks a rigorously defined semantics for its models, which makes formally ana-lyzing a model, verifying its properties, testing it and generating code from it extremely difficult. Action semantics is a newly developed language aimed at precisely describing the behavior of programs and models. It is a desirable extension to UML. The history of action semantics, including the pros and cons of its predecessor, denotational semantics, is briefly introduced. Comparison is made on different attempts to achieve an executable UML. The basics of action semantics, including all the defined action types, is discussed in detail. From this discussion, the conclusion is drawn that, though flaws still exist, action semantics is a powerful tool to describe behavior in the level of both modelling and meta-modelling. 1 Introduction to Action Semantics Action semantics is a newly developed language aimed at precisely describing the behavior of programs and models. It starts from modifying denotational semantics, but finally ends up with a completely new semantics, which is much more modular and extensible than its predecessor. 1.1 Denotational semantic