Case modeling is a part of UML modeling and the most basic part of UML. The main function of case modeling is to express the functional requirements or behaviors of the system. To put it bluntly, it is to explain what the system is, so you don't have to worry about how to work. I think the use case chart is the best picture in the analysis phase, because the content is very macro.
Understand the elements in the use case diagram:
- Role)It is an entity that interacts with use cases in the system. In actual situations, the role can be a person or another system or hardware device. In the process of drawing a use case diagram, the role is often the first to be determined, because the system or use case is vague at the beginning, but the role involved in the system is the easiest to clarify. After a role is created, the system and use cases can be further determined based on the interaction between the role and the system and the functions required by the role.
- Use Case)It refers to the system function, which is a collection of all the execution actions of a function of the system. In the UML diagram, it is an elliptic, but all the steps to execute the action of the use case must be given during the analysis of the use case.
- System)It refers to a software system. It can contain some use cases and define the boundaries of the system. The functions and actions within the boundary belong to the system, and those outside the boundary are not the system's concerns. The system specifies a black box with certain functions. What you see outside the system is only the functions of the system, rather than the internal details of the system. It can also be called a topic.
Case Description:
Use case description generally includes: Brief description (description), prerequisite conditions, basic event stream, other event streams, abnormal event streams, and post (post) conditions.
- Brief Description: A brief description of the role and purpose of the use case;
- Prerequisites: The State or conditions that must be met before the execution of the use case;
- Basic event stream: Describes the basic process of this case. It refers to what happens when every process is "normal". There is no alternative stream or abnormal stream, but only the most likely event stream;
- Other event streams: Indicates that this action or process is optional or optional, and it is not always necessary to execute them;
- Abnormal event stream: Indicates the process to be executed when an abnormal event occurs;
- Post Condition: The status of the system after the use case is executed;
Relationship between use cases:
IncludingAssociation, inclusion, extension, and GeneralizationFour relationships.
it is easy to understand these relationships. Association indicates communication between two use cases.
A use case contains the functions and behaviors of another use case.
expansion is to add new functions on the basis of the Basic use case, which is defined as the incremental expansion of the basic use case.
generalization is the inheritance relationship we are familiar.
