On the use case diagram of UML learning notes

Recently has been learning the basic knowledge of UML, after watching the video, and did not have a good summary, in the process of drawing found a lot of problems, the following is the process of reading their own summary of the UML use case diagram of a little knowledge, share with you.

First, the concept

A use case diagram is a dynamic view of the actors, use cases, and their relationships that describe the functionality of the system.

A use case is a functional unit in a system that describes what a system does (what) and not how to do it. Use case diagrams describe the relationship between actors and use cases, indicating which use cases are used by users of the system.

Second, the composition

The concept of use case diagrams, we learn through a graph:

We focus on the association between use cases in the use case composition: including

"Presentation" dashed arrow + include; Arrows are pointed to the included use case by the underlying use case

"function" improves maintainability of use case model; simplified description avoid repeating the same behavior in multiple use cases or inconsistent description of the same paragraph behavior

"Include diagram" extension

"Presentation" dashed arrow + extend; arrow pointing to base use case

"Action" under certain conditions, the extension use case adds new behavior to the underlying use case

Extension Map generalization

"Representation" Solid line empty triangle arrow; arrow pointing to parent use case

The "action" sub-case inherits all the structure, behavior, and relationships of the parent use case, which is a special form of the parent use case

"Generalization map"

Comparison of extended relationships and containment relationships:

1. Extended relationship: The underlying use case provides one or more insertion points, and the extension use case provides the insertion point with the desired behavior

Contains only one insertion point in a relationship

2. Extended relationship: Basic use case execution, extension not necessarily executed

Include relationship: Basic use case execution, including use case must be executed

3, extended relationship: Even if there is no extension use case, the underlying use case itself is complete

Include relationship: No use case, the underlying use case itself is incomplete

For everyone to simply give a small example of the computer room charge system: