UML Unified Modeling Language Learning Notes

Unified Modeling Language (UML) also known as Unified Modeling Language or standard modeling language

I. The role of UML

1. Ability to look at the structure, behavior, and function (requirements) of the system from different angles. 2. It is not enough to be able to think about the system at different levels of abstraction, but only the source code. Source code is a very granular internal structure that cannot be used to build complex systems. ii. definition of UMLThe definition of UML includes two parts of UML semantics and UML notation. UML semantics: Describes the definition of exact meta-model based on UML. The meta-model provides simple, consistent, and generic definitions for all elements of UML in syntax and semantics, enabling developers to achieve semantic consistency and eliminate the impact of the best expression methods that vary from person to person. In addition, UML supports extended definitions of meta-models. UML notation: Defines the representation of UML notation, which provides a standard for developers or development tools to use these graphical symbols and text syntax. These graphical symbols and literals express the application-level model, which is semantically an instance of the UML Metamodel.Third, the purpose of using UML diagram at different stages

when you ...	use UML diagram ...
	use case diagrams, which contain entities that interact with the system and require real The current function point.
	activity diagrams, which focus on the workflow of the problem domain (people and the actual space in which other principals work, the subject domain of the program), rather than the logical flow of the program.
Observe object interaction	interaction diagram, which shows the specific object and how it interacts. Because they deal with specific cases rather than the general situation, they can be useful in testing requirements and testing designs. The most popular interaction diagram is the sequence diagram.
in the design phase
Observe the behavior of the object, which differs depending on the state of the object
in the deployment stage	layout diagram showing how different modules will be deployed. I will not discuss them here.

iv. Definitions and examples of five types of UML diagrams (9 graphs in total)1. Use case diagrams: Describe the system function from the user's point of view, and indicate the operator of each function .

"Concept" describes the user's needs and describes the functions of the system from the user's perspective.

The "Descriptive Way" ellipse represents a use case; a humanoid symbol denotes a role

"Purpose" helps group development teams understand the functional requirements of the system in a visual way

"Use case diagram"

2. Static diagram: Includes class diagram, object graph and package diagram.

1) Class diagram: Describes the static structure of classes in the system. Defines not only the classes in the system, but also the relationships between classes, such as associations, dependencies, aggregations, and the internal structure of the class (properties and operations of the class). A class diagram describes a static relationship that is valid throughout the life cycle of the system.

"Concept" shows the static structure of the system, indicating how different entities are associated

"description" three rectangles

"Purpose" represents a logical class or implementation class, which is usually the object of the user's business; The implementation class is the entity that the programmer processes

"Class Diagram"

2) object graph (Diagrams): An object graph is an instance of a class diagram. An object graph is an instance of a class diagram that uses almost exactly the same identity as the class diagram. Their difference is that the object graph shows multiple object instances of the class, not the actual class.

An example of a "concept" class diagram that describes the objects that the system contains at a specific point in time and the relationships of the individual objects

"Object Graph"

Third, behavior diagram (Behavior diagram): Describes the dynamic model of the system and the interaction between the constituent objects.

1) state diagram: Describes all possible states of an object of a class and the transition condition of the state when an event occurs.

"Concept" describes the transition between all States of an object and the state caused by the occurrence of an event

"How to Describe"

1. Starting point: Solid Circle
2. Transitions between states: segments with open arrows
3. Status: Rounded Rectangle
4. Judging point: Hollow Circle
5. One or more end points: a circle with a solid circle inside it

"Purpose" indicates the different states in which a class is located and the process in which the class is converted in these states

2) Activity diagram: Describes the activities to meet the use case requirements and the constraints between activities to facilitate identification of parallel activities.

"Concept" describes the activities that are required to meet the use case requirements and the constraints of the active time

"How to Describe"

1. Starting point: Solid Circle
2. Activity: Rounded Rectangle
3. End point: a circle with a solid circle inside it
4. Swimlane: The object that actually executes the activity

"Purpose" represents the process control process between two or more objects when an activity is processed

"Activity diagram"

Activity diagram and state diagram differences:

Iv. interaction Diagram (Interactive diagram): Describes the interaction between objects.

1) Sequence diagram: Shows the dynamic partnership between objects, which emphasizes the order in which messages are sent between objects, and shows the interaction between objects

2) Cooperation diagram: Describe the collaborative relationship between objects. In addition to displaying information exchange, the collaboration diagram also shows the objects and their relationships. If the emphasis is on time and order, then the sequence diagram is used, and if the subordinate relationship is emphasized, the collaboration diagram is selected. These two kinds of graphs are called interaction graphs.

V. Implementation diagram (Implementation diagram):

1) Component diagram: Describes the physical structure of the code part and the dependencies between the components. A part may be a resource code part, a binary part, or an executable part. It contains information about a logical class or implementation class.

"Concept" describes the physical structure of code artifacts and the dependencies between components

Description Method Widget

"Purpose" provides a physical view of the system, displaying the entire physical structure of the system code according to the code component of the system

"Architecture Diagram"

2) Part diagram: Helps to analyze and understand the degree of interaction between parts.

Physical architecture of hardware in a "conceptual" system

"How to Describe"

1. Three-dimensional cubes represent parts
2. Node name in Upper Cube

"Purpose" displays the physical structure of the system's hardware and software

"Deployment Diagram"

UML Unified Modeling Language Learning Notes