The document discusses UML with action semantics (xUML), which allows UML models to be executed. It covers key concepts like actions, which are the fundamental unit of computational behavior, and action semantics, which remove assumptions about specific computing environments. xUML models can be used to define executable analysis models. The document also provides an overview of behavioral modeling elements in UML like use cases, and covers the action metamodel which defines how actions work through inputs, outputs, data flow, and control flow. It distinguishes between primitive actions and procedures as an action container.