Use Case chart-do you understand it?

Generally, when we introduce a thing, we will discuss the problem from three perspectives: what it is, why, and how it is. For our Use Case chart, in addition to these three aspects, we also need to add a question about when to draw. However, these knowledge are basic things, and there is a lot of information on the Internet. This article will not go into detail. So what should I talk about in this article? We will analyze the use case diagram in depth, focusing on the relationship between the use case diagram and several other diagrams, or the relationship between the use case diagram and the program.

 

First, we use an example to lead everyone into the world of UML.

It is the most common overall structure of the Software. We will take this structure as an example to illustrate the relationship between the use case diagram and other diagrams.

It is a simple data center management use case diagram. For your convenience, I will use Chinese for the case name. Data center administrators can perform on-machine and off-machine operations.

The use case diagram focuses on how to describe the system. How can these methods be reflected? Next, let's take a look at the computer management class in the facade (appearance Layer.

From the above two figures, we can see that the use cases in the use case diagram correspond to the methods of classes in the facade one by one.

Next, we will continue to refine the use case diagram.

Let's take a look at the class methods in bllmanager (business logic layer.

From the above two figures, we can see that the refined use cases correspond to the class methods in bllmanager one by one.

Use case diagram after perfection:

The sequence chart corresponding to the machine operation:

The time sequence diagram is the embodiment of the program code. As a result, the use case diagram is transferred to the code implementation step by step.

Through the example above, what do I want to explain? The use case diagram focuses on the description of the system method, while the coarse-grained use case diagram basically corresponds to the method of the appearance layer. The further refined use case diagram basically corresponds to the method of the business logic layer. How are classes in the appearance layer and business logic layer generated? These classes are formed after the classification and synthesis of methods. The sequence diagram shows the call relationship between classes at different layers, which eventually forms the program code. Of course, the use case diagram is closely related to the menu at the interface layer.

To sum up, the use case diagram plays a vital role in the entire program development process. I think that the use case diagram occupies the dominant position in the nine UML diagrams. Do you really understand this important use case diagram?