UML is a unified modeling language. Its concept is: (1) UML is the standard language of writing software blueprints; (2) UML is specified, constructed, and recorded software as the primary system.
UML is a full-faced object, which is graphically, which provides different levels and angles for different participants developed by the system;
The main maps provided by the UML are: class diagrams, object maps, use case diagrams, state diagrams, timing charts, active diagrams, collaboration diagrams, components diagrams, and deployment diagrams. The most important and use of the most three patterns are used in the case (the user case diagram), the secquency diagram and class diagram. The use case is a diagram of describing the external function of the system from the user's angle. For different users, the system should have different functions, so the example of the use of a system usually has multiple. The timing diagram is an angle to be implemented from the system to each use case, and it can be seen that one case general should generally have a corresponding timing chart. It describes the relationships and sequences of messaging between users in a use case to communicate between messaging, and system components (class). The timing chart represents the statically logic of the system implementation, which can directly connect directly to the specific implementation logic of a module in the code, so it is most important to system logic. The class diagram corresponds directly to the source code. In object-oriented programming, the entire system is implemented by classes and their instances (objects) by transmitting messages between each other and their respective message processing functions. The timing diagram describes the messages to be sent between the individual classes, and the class diagrams indicate how to send, receive, and process these messages, which include various attributes and methods.
To draw this 3 type diagram, especially when starting, it is not practical. It is often a guide to the analysis and design of the system, and all the pictures are not fully drawn. UML is just a design method, and it should not be perfect when designing.
