UML-Unified Model Language Unified Modeling Language , also known as Standard Modeling Language. is a language for visual modeling of software -intensive systems. There are three main models in UML system development: Functional Model: Shows the functionality of the system from the user's point of view, including use case diagrams. Object Model: Use concepts such as objects, properties, operations, and associations to display the structure and foundation of the system, including class diagrams , object diagrams, and package diagrams. Dynamic Model: Shows the internal behavior of the system. Including sequence diagrams, activity diagrams, state diagrams.
The important content of UML can be defined by the following five kinds of diagrams
Use Case Diagram : Describes system functions from the user's perspective and refers to the operators of each function.
Static diagrams : including class diagrams, package diagrams, and object diagrams.
Class Diagram: Describes the static structure of classes in the system
Package diagram: It is composed of packages and classes, representing the relationship between packages and packages, and the package diagram describes the hierarchical structure of the system
Object Diagram: is an instance of a class diagram
Behavior diagram : Describes the exchange relationship between the dynamic model of the system and the composition of objects. Including state diagrams and activity diagrams
Activity diagram: Describes the workflow of the business to realize the use case
State diagram: is to describe the state-to-state control flow, often used for dynamic characteristic modeling
Interaction diagram: describe the interaction between objects
Sequence diagram: Dynamic cooperation between objects, emphasizing the order in which objects send messages, while showing interactions between objects
Collaboration diagram: describe the assisting relationship between objects
Implementation diagram:
Configuration diagram: defines the physical architecture of the hardware and software in the system
UML includes use case diagram, class diagram, component diagram, deployment diagram, sequence diagram, collaboration diagram, state diagram, activity diagram
Introduction to each figure:
A use case diagram captures the behavior of a system from the perspective of an external user. He divides system functions into transactions that are meaningful to actors.
Class diagrams are diagrams that describe classes, interfaces, writing, and the relationships between them
A sequence diagram describes a series of messages arranged over time. Each classified role is displayed as a lifeline, representing the role throughout the interaction. Messages appear as arrows between lifelines.
Collaboration diagrams model objects and chains of meaning in interactions
A state diagram is used to describe all possible states of a specific 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 presents a functional model diagram of the system that external users can observe.
[Purpose]: Help the development team understand the functional requirements of the system in a visual way.
The elements included in the use case diagram are as follows:
1. Actor
Represents a user, organization, or external system that interacts with your application or system. Represented by a small person.
2. Use Case
A use case is an externally visible system function that describes the services provided by the system. represented by an ellipse.
3. Subsystem
It is used to show part of the function of the system, and this part of the function is closely related.
4. Relationship
The relationships involved in the use case diagram are: association, generalization, inclusion, and extension.
As shown in the table below:
a. Association
Represents a communication between an actor and a use case, either party can send or receive messages.
【Arrow point】: point to the recipient of the message
b. Inheritance
Inheritance relationship is commonly understood, child use case is similar to parent use case, but exhibits more special behavior; child use case will inherit all the structure, behavior and relationship of parent use case. A child use case can use a piece of behavior from the parent use case or override it. Parent use cases are usually abstract.
【Arrow points】: point to the parent use case
c. Include
Inclusion relationships are used to break down the functionality represented by a more complex use case into smaller steps.
【Arrow pointing】: Point to the decomposed functional use case
d. Extend
The extension relationship refers to the extension of the function of the use case, which is equivalent to providing an additional function for the basic use case.
【Arrow pointing to】: Point to the basic use case
e. Dependency
The above four relationships are standard relationships defined by UML. However, in the use case model diagram of VS2010, a dependency relationship is added, which is represented by a dotted line with an arrow, indicating that the source use case depends on the target use case.
[arrow pointing to]: point to the dependent item
5. Artifact
Although use case diagrams are used to help people understand functional requirements visually, not many people can understand them. In many cases, communicating with users and even using Excel is better than use case diagrams. In VS2010, an element such as "project" was introduced to allow developers to link a common document in the use case diagram.
Use dependencies to depend on a use case on a project:
Then set the Hyperlink of the project->property to your document;
This way when you double-click an item on the use case diagram, the associated document will open.
6. Comment
The difference between include (include) , extension (extend) , and generalization (Inheritance) :
Conditional: sub-use cases in generalization and included use cases in include will occur unconditionally, while the occurrence of extended use cases in extend is conditional;
Directness: Sub-use cases in generalization and extension use cases in extend provide direct services to actors, while use cases included in include provide indirect services to actors.
For extend, the extended use case does not contain the content of the base use case, and the base use case does not contain the content of the extended use case.
For Inheritance, a sub-use case contains all the content of the base use case and its relationship to other use cases or actors;
An example use case diagram:
