Ranking of various graphical importance in UML

Martin Fowler divides the importance of various diagrams in UML so that we don't have to spend months getting familiar with all the details of UML, instead, you only need to read two or three chapters of the content to obtain great value from UML.

The ranking of various graphical importance in UML is:
Use case diagram)
Class Diagram)
Sequence)
Collaboration)
Package)
Status chart (state)
Activity diagram)
Physical graph (physical)

Only use case charts and class charts are required. The use case diagram is important because it is the basis of object-oriented analysis design, and case-driven is the main feature of various modern development methods such as RUP and XP, class diagrams are important because they are the most important tool for analysis and design.

Class Diagrams have the most abundant connotations among various UML diagrams. However, the rich connotations also make it difficult to correctly use class diagrams. Martin specifically divided the concept of a class chart into two parts: the basic part and the advanced part. The basic part is very simple. In many cases, the basic part is enough and must be used only when necessary.