UML Series Diagram-use case diagram

Uml-unified Model Language Unified Modeling Language, also known as standard modeling language. is a language used to visualize modeling software-intensive systems.

There are three main models in UML system development:

Functional Model: Display the function of the system from the user's point of view, including use case diagram.
Object model: Using the concepts of object, attribute, operation and correlation to show the structure and foundation of the system, including class diagram, object graph and package diagram.
Dynamic model: Show the internal behavior of the system. Including sequence diagram, activity diagram, State diagram.

The important content of UML can be defined by the following five kinds of graphs

use case Diagram : Describes the system function from the user's point of view and refers to the operator of each function.

static diagram : Including class diagram, Package diagram, object graph.

Class diagram: Describing the static structure of classes in a system

Package diagram: Is the package and class composition, representing the relationship between the package and the package, package diagrams describes the hierarchical structure of the system

Object graph: An instance of a class diagram

Behavior Graph : Describes the exchange relationship between system dynamic model and object composition. Include Statechart and activity diagrams

Activity diagram: Describes the workflow of a business implementation use case

State diagram: Describes state to state control flow, often used for dynamic modeling

interaction Diagrams: describing the interaction between objects

Sequence diagram: Dynamic partnership between objects, emphasizing the order in which objects send messages, and showing the interaction between objects

Collaboration diagram: Describe the assistance relationship between objects

Implementation diagram:

Configuration diagram: Defining the physical architecture of hardware and software in a system

UML includes use case diagrams, class diagrams, Component diagrams, deployment diagrams, Sequence diagrams, collaboration diagrams, State diagrams, activity diagrams

Introduction to each diagram:

A use case diagram captures the behavior of the system from an external user's perspective. He divides the system functionality into transactions that are meaningful to the active person.

Class diagrams describe graphs of classes, interfaces, writing, and the relationships between them

The sequence diagram describes a series of messages that are scheduled over time. Each category role is displayed as a lifeline that represents the role during the entire interaction. The message is displayed as an arrow between lifelines.

Object and chain modeling of the existence meaning of collaborative graphs in interaction

A statechart diagram is used to describe all possible states of a particular object and the transitions and changes between states due to the occurrence of various events.

Use case diagrams are mainly used to describe the relationship between users, requirements, and system functional units. It shows a system function model diagram that an external user can observe.

"Purpose": helps the development team understand the functional requirements of the system in a visual way.

The use case diagram contains the following elements:

1. Participants (Actor)

Represents a user, organization, or external system that interacts with your application or system. expressed by a villain.

2. Use Cases

A use case is an externally visible system function that describes the services provided by the system. represented by an ellipse.

3. Subsystem (SUBSYSTEM)

Used to show a part of the system's functionality, which is closely related.

4. Relationship

The relationships involved in a use case diagram are: Association, generalization, inclusion, extension.

As shown in the following table:

A. Association (association)

Represents communication between a participant and a use case, and either party can send or receive messages.

"Arrow pointing": Pointing to message receivers

B. Generalization (inheritance)

Is the inherited relationship that is commonly understood, and the child case is similar to the parent case, but behaves more specifically; the child use case inherits all the structure, behavior, and relationships of the parent use case. A child case can use a behavior of a parent use case, or it can be overloaded. The parent use case is usually abstract.

"Arrow pointing": pointing to the parent use case

c. Inclusion (include)

　　 The containing relationship is used to break down the functionality represented by a more complex use case into smaller steps.

"Arrow pointing": Pointing to the decomposed feature use case

d. Extension (Extend)

An extended relationship is an extension of the function of a use case, which is equivalent to providing an additional function for the underlying use case.

"Arrow pointing": pointing to the underlying use case

E. Reliance (Dependency)

The above 4 relationships are the standard relationships of UML definitions. However, in the VS2010 use case Model diagram, a dependency is added, represented by a dashed line with an arrowhead, indicating that the source use case is dependent on the target use case.

"Arrow pointing": pointing to a dependency

5. Project (artifact)

Use case diagrams are designed to help people visualize functional needs, but few people can understand it. Most of the time you communicate with users and even Excel is more powerful than use case diagrams, VS2010 introduces an element such as "project" so that developers can link to a common document in a use case diagram.

To rely on a use case for dependencies on a project:

Then set the hyperlink of the project-"attribute" to your document;

This opens the associated document when you double-click the project on the use case diagram.

6. Note (Comment)

the differences between include (include), extension (extend), generalization (inheritance):

Conditional: In the generalization of the child use cases and included in the inclusion of the use of the meeting unconditionally, while the extension use case in extend is conditional;

Directness: The extension use case in generalization and in extend provides direct service to participants, while the use cases included in include provide indirect services to participants.

For extend, the extension use case does not contain the content of the underlying use case, nor does the underlying use case contain the content of the extension use case.

For inheritance, a child case contains all the content of the underlying use case and its relationship with other use cases or actors;

A Use case diagram example: