It is now part of the software trade. The UML gives everyone from business analyst to designer to programmer a common vocabulary to talk about software design. The UML is applicable to object-oriented problem solving. A model is an abstraction of the underlying problem. The domain is the actual world from which the problem comes.
Models consist of objects that interact by sending each other messages .
The values of an object's attributes determine its state . Objects are instances of classes. Use case diagrams Use case diagrams describe what a system does from the standpoint of an external observer. The emphasis is on what a system does rather than how. Use case diagrams are closely connected to scenarios.