UML object-oriented analysis and modeling-[3] use case diagram

I,Description of the use case diagram

Use Case (Use Case) Refers to the interaction between the system's external things (activists, devices, or external systems) and the system. It expresses the functions of the system, that is, the services provided by the system.

A Use Case chart is a visualization tool used to describe use cases. It uses simple graphical elements to represent the system's activists, use cases, and their relationships, accurately expresses the interaction between the operator and the system and the services that the system can provide. The use case diagram describes the requirements for software products from the user perspective rather than from the developer perspective, and analyzes the functions and dynamic behaviors required by the products.

II,Operator

Determine the operator. The operator can define the generalized relationship.

1.Who are the main customers of the system?

2.Who gets information from the system?

3.WHO provides information to the system?

4.Who will install and operate the system?

5.Who will shut down the system?

6.Is there a time automatic at the scheduled time?

7.Who uses or deletes information in the system?

8.Where the system obtains information

III,Case Description

The use case description is a type description about how roles interact with the system. The specification is clear and unambiguous. Generally, the use case description includes The purpose of the use case, how the use case is started, the message stream between the use case and the activity, the multiple execution plans of the use case, and how the use case is completed, and the value is passed to the activity. The use case description can be implemented using the use case template.

 

Use Case Template

Case name(Use Case name)

Case objective(Objective of the use case in the System)

Level(Summary task)

Operator(The operator of this use case)

Status

PrerequisitesSystem status before case execution

Post ConditionStatus of the system after successful use case execution

Master pathName of the main path of the use case

Optional pathOptional use case path

Exception pathUse Case exception path

 

IV,Relationship between Use Cases

In addition to being associated with the active users, the use cases also have some relationships, including generalization, usage, inclusion, and extension.

V,Case Modeling

To create a Use Case chart, follow these steps:

1.Determine the boundaries and scope of the system, and clarify the operators and external systems outside the system.

2.Determine the expected system behavior of each operator.

3.Use these system behaviors as system use cases.

4.Common system behaviors are decomposed into new use cases for reference by other use cases. The change behavior is divided into extended use cases.

5.Compile the script for each use case.

6.Use Case chart.

7.Identifies the main business flow and event streams with exceptions. Use Cases that express abnormal event streams can be drawn into a separate sub-use case diagram.

8.Refined use case diagram. Solves the problem of repetition and conflict in the use case diagram, and simplifies the conversation sequence in the use case. High-level use cases can be divided into use cases in several subordinate subsystems.

VI,Example

In the book management system, the staff can maintain (add, delete, and update) reader information, and maintain book information. Readers can request to borrow, return, and renew books through the Book Administrator, readers can log on to and query books and borrowing information. The example graph is provided.

 

References:

[1] Tang xuezhong and others . UML Object-Oriented Analysis and Modeling . Electronic Industry Press . 2008

[2]Cai min waited. UMLBasic andRoseModeling tutorial.People's post and telecommunications Publishing House. 2006

[3] Carlo ghezzi Waiting . Shi ping'an Translation . Software Engineering Basics ( The 2 Version ) Tsinghua University Press . 2003

[4]Reference website:

Http://www.omg.org/UML

Http://www.rational.com/UML

Http://www.software.ibm.com/ad/ocl