Today some evidence arises that UML will more and more be used not as a specification language but as a high level programming language. This has some advantages, as if the concepts of UML are executable, they can immediately be animated and tested, or the generated code even be used as implementation. Thus UML probably will have an implementation-oriented semantics describing this animation.

Bernhard Rumpe (1998) "A Note on Semantics (with an Emphasis on UML)." Proceedings of Second ECOOP Workshop on Precise Behavioral Semantics. 1998.