Executable UML, often abbreviated to xtUML or xUML, is the evolution of the Shlaer-Mellor method to UML. Executable UML graphically specifies a system using a profile of the UML. The models are testable, and can be compiled into a less abstract programming language to target a specific implementation. Executable UML supports MDA through specification of platform-independent models, and the compilation of the platform-independent models into platform-specific models.

Executable UML is used to model the domains in a system. Each domain is defined at the level of abstraction of its subject matter independent of implementation concerns. The resulting system view is composed of a set of models represented by at least the following:

  • The domain chart provides a view of the domains in the system, and the dependencies between the domains.
  • The class diagram defines the classes and class associations for a domain.
  • The statechart diagram defines the states, events, and state transitions for a class or class instance.
  • The action language defines the actions or operations that perform processing on model elements.

Shortcomings of Executable UML

UML doesn’t define semantics of a programming language. Hence, it is not complete to describe behavior of any exact system. In order to correct this shortcoming some new principles are needed. Some of them are: automata theory and symbol-driven engineering.

Automata Theory and Symbol-Driven Engineering (SDE)

Automata theory defines behavior model for corresponding code elements. Therefore, this theory background  eliminates the gap between program behavior and the corresponding model, like UML

In SDE every symbol has an automaton behind it. In order to execute those symbols an invocation Symbol:run is needed plus some specific initailizations for some specific symbols like definitions (method invocations and  object and variable definitions). See figure below.

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