Unified Modeling Language (UML) is a standardized general-purpose language. Object Management Group created and manages the standard.
UML is used in generating artifacts of an object-oriented software-intensive system along with offering a way to view a system's architectural blueprint.
UML is not a development method by itself. It was designed to be compatible with the leading object-oriented software development methods of its time. Since UML has evolved, some of these methods have been recast to take advantage of the new notations (for example OMT), and new methods have been created based on UML, such as IBM Rational Unified Process (RUP). Others include Abstraction Method and Dynamic Systems Development Method.
It is important to distinguish between the UML model and the set of diagrams of a system. A diagram is a partial graphic representation of a system's model. The model also contains documentation that drives the model elements and diagrams UML Diagrams represent two different views of a system model.
Static (structural) view: emphasizes the static structure of the system using objects, attributes, operations and relationships. The structural view includes class diagrams and composite structure diagrams.
Dynamic (behavioral) view: emphasizes the dynamic behavior of the system by showing collaborations among objects and changes to the internal states of objects. This view includes sequence diagrams, activity diagrams and state machine diagrams.
Models can be exchanged among UML tools by using the Extensive Markup Language interchange (XMI) format. There are different versions of the XMI standard and that there are different levels of compatibility between the various UML tools.