Class diagram (Class diagram) Is to show the static structure of the model , Especially the classes that exist in the model , The internal structure of classes and their relationship with other classes . Class diagrams do not display transient information . Class diagram is the main component of object-oriented modeling . It is used for general conceptual modeling of application system classification , Also used for detailed modeling , Converting the model into programming code . Class diagrams can also be used for data modeling .
Class diagram is mainly used in the analysis and design phase of object-oriented software development , Describe the static structure of the system . The class diagram illustrates all the entities of the built system , The internal structure of entities and the relationship between entities . Namely ． The class diagram contains classes abstracted from the user's objective world model , The internal structure of classes and the relationship between classes . It is the basis for building other design models , There is no class diagram , There is no object graph , state diagram , Collaboration map, etc UMI． Dynamic model diagram ． The dynamic behavior of the system cannot be represented . Class diagram is also the starting point and basis of object-oriented programming .
The role of class diagram ：
（1）： In software engineering , Class diagram is a static structure diagram , Describes the collection of classes of the system , The properties of a class and the relationships between classes , It can simplify people's understanding of the system ;
（2）： Class diagram is an important product of system analysis and design , It is an important model of system coding and testing .