UML (Unified Modeling Language) is a standard notation for the modeling of real-world objects as a first step in developing an object-oriented design methodology. Its notation is derived from and unifies the notations of three object-oriented design and analysis methodologies:
Grady Booch's methodology for describing a set of objects and their relationships
James Rumbaugh's Object-Modeling Technique (OMT)
Ivar Jacobson's approach which includes a use case methodology