The document discusses the need for an executable version of the Unified Modeling Language (UML) called xUML. It notes that while UML 1.x describes system behavior, it is not fully executable because it lacks precise semantics for actions. xUML addresses this by defining a precise action semantics language and process to allow UML models to be executed, validated, and automatically generated into code. An executable UML provides benefits like early verification of requirements, improved quality through objective criteria, and more fun for analysts.