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In our work, we often describe the content of the project to others, explain the operation of a function, and so on. In addition to the text description, it is illustrated in conjunction with the diagram, which increases the ability to visualize the problem and facilitates communication and understanding. At the beginning, I always wanted to use one kind of diagram to express everything, but in fact, no kind of graph can do it, and even if it can be done, it will make this kind of diagram complicated and not in line with human acceptability. It would be nice to use the corresponding diagram to illustrate the corresponding problem. Introduce several kinds of pictures that I often use.

1. Use case diagram application scenario: used to describe the relationship between system participants and functional use cases, reflecting the overall operation of the system and interaction design. Construction process: first model the system function, and then determine the behavior of the role, that is, the relationship between the role and the function, including some role attributes, according to the system role involved in each function, but the use case diagram does not express the attributes obviously. In general, use cases describe the responsibilities of roles in the system, their relationships with important functions in the system, and roles and functions.

Examples are as follows:

two。 Flow chart

What is the flow chart (Flow Chart): as the name implies, it is used to visually describe the specific steps of a workflow diagram, it usually uses some boxes to represent various types of operations, write out the various steps or judgment conditions in the box, and then connect them with arrowhead lines to show the order of implementation, using graphics to represent the implementation steps, very intuitive, easy to understand. The following left picture shows the standard flowchart components in visio software, and the right figure shows an example of the flowchart.

3. Time sequence diagram

It represents the sequence of messages between classes, components, subsystems or participators. it actually describes in detail, directly and rigorously, the order in which a function or process is executed in time, the horizontal axis is the role or component, and the vertical axis is the time axis. Each of these messages corresponds to a class operation or trigger event in the state machine that causes the transformation.

The description of the timing diagram in visio:

There are also these items in the timing diagram: Actor, Object, lifeline, Activation, and Message.

Role (Actor)

System roles, represented by a villain icon, can be people or other systems or subsystems.

Object (Object)

The object is located at the top of the timing diagram and is represented by a rectangular block

Lifeline (LifeLine)

Each object and the center of the bottom in the timing diagram has a vertical dotted line, which is the lifeline of the object (the timeline of the object). With a vertical dotted line table.

Control focus (Activation)

The control focus represents the actions performed in the sequence diagram during a certain period of time on the object timeline. Represented by a very narrow rectangle.

Message (Message)

Represents the information sent between objects. There are four types of messages.

Synchronous message (Synchronous Message): the sender of the message passes control to the recipient of the message, then stops activity and waits for the recipient of the message to give up or return control. Represented by a solid line + solid arrow.

Asynchronous message (Asynchronous Message): the sender sends a signal to the recipient of the message through the message, and then continues its own activities without waiting for the recipient to return the message or control. The receiver and sender of asynchronous messages work concurrently. Represented by a solid line + hollow arrow.

Return message (Return Message): the return message indicates that it is returned from the procedure call. Indicated by a dotted hollow arrow.

Self-associated message: represents a method's own call or a method within an object calling another method. Represented by a semi-closed solid line solid haircut.

The following picture shows the timing of Wechat transactions. Please pay attention to the blue block comments.

4. Component diagram / class diagram

In order to avoid the process of this article, we will not introduce the component diagram and class diagram in detail, because if they want to understand, they both need and deserve a separate article to introduce. Let's introduce his usage scenarios and examples to illustrate.

Component diagram: a UML diagram describing the relationship between components and components in a software system, withdrawing an implementation structure, also known as component diagram.

Class diagram: a diagram commonly used in software systems to describe the relationship between classes. Generalization (Generalization), implementation (Realization), Association (Association), Aggregation (Aggregation), Composition (combination), Dependency (relationship) are used to describe the relationship between classes in the system. Because a class in a software system often has many associated classes and derived classes, it is difficult to describe its three-dimensional relationship by relying on language alone.

5. Mind map

Put this at the end because it is not a technology-related diagram, in fact, the mind map and the outline list do the same thing (generally speaking, they can be converted to each other), many people have come into contact with it, and it is relatively easy to apply. I'm not going to show it either.

Mind map: often used to organize their own ideas, to facilitate their own systematic memory. It has a strong hierarchical relationship and spreads from one point to another, which is helpful to people's thinking exercise and planning.

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