Class Diagram for LinkedIn

In this lesson, we’ll identify and design the classes, abstract classes, and interfaces based on the requirements we have previously gathered from the interviewer in our LinkedIn system.

Components of LinkedIn#

As mentioned earlier, we will design the LinkedIn system using a bottom-up approach.

Account#

The Account class identifies a LinkedIn user through their username and ID. Users with an account will have the option to create groups, pages, posts, comments, and like other comments and posts.

The class definition is represented below:

Education, experience, and skill#

The Education, Experience, and Skill classes provide relevant information and make up the Profile class.

These classes are represented below:

Recommendation, achievement, and analytics#

The Recommendation, Achievement, and Analytics classes are used to provide relevant information and make up the Profile class.

These classes are represented below:

Profile#

The Profile class contains the personal information of a LinkedIn user—their profile, cover photo, experiences, education details, skills, and achievements.

The visual representation of the Profile class is given below:

Company page, job, and group#

The CompanyPage class represents a particular page for a company that exists on LinkedIn. It contains the name, description, company size, etc.

The Job class contains information about a job posting at a specific company and current job openings.

The Group class represents a particular group that exists on the LinkedIn platform. This will contain the name, description, total users, and a particular ID to uniquely identify the group.

The representation of these classes is given below:

Post, comment, and message#

The Post class indicates a post made by a user. It contains information regarding its content, the number of reacts and shares of the post, and the owner of the post.

The Comment class indicates a comment made by a user on a post. It includes information regarding its content, the number of reacts, and the owner of the comment.

The Message class represents the message sent by a user to other users. Therefore, it contains the content and multimedia elements like images or videos.

The representation of the classes is shown below:

Connection invitation#

The ConnectionInvitation class describes the details of a connection invitation. It will contain the status of the connection invite and the methods that indicate whether the request was accepted or ignored.

The class diagram of the ConnectionInvitation class is shown below:

Person#

The Person is an abstract class that contains details like the name, address, phone number, and email. It is derived into the Admin and the User class.

Admin

The Admin class is responsible for performing operations such as blocking or unblocking users.

User

The User class is the main class of LinkedIn. It is responsible for making various kinds of operations such as applying for jobs, sending messages or friend requests to other users, creating posts and pages or joining groups, and numerous other operations.

These three classes are represented below:

Notification#

The Notification class sends a notification using the built-in notification option. It is mainly responsible for sending notifications whenever any of the following conditions are met:

• A connection invitation is received.

• A new message is received.

• A new comment is added to a post that a user has created or is following.

• A new post has been created by a user or a company page that another user is following.

The UML representation of the class is shown below:

Search interface and search catalog#

The Search interface allows users to search for any particular user, company, group, and job opening. It also returns the list of respective components.

The search functionality is implemented using the SearchCatalog class. The catalog will contain a list of users, pages, and jobs, and can add new users, pages, and jobs to the catalog.

The representation of the SearchCatalog class and the Search interface is given below:

Enumerations#

The enumerations required in the LinkedIn design are provided below:

• AccountStatus: The account status tells us about the status of a user's account, i.e., whether it is active, deactivated, or blocked.

• ConnectionInviteStatus: The connection invite status describes the status of a connection invitation—whether it is pending, accepted, or ignored.

• JobStatus: The job status describes the current status of a job posting—whether it is open, on hold, or closed.

Custom data type#

We need to create a custom data type, Address, which stores the location of a LinkedIn user.

Relationship between the classes#

Now, we’ll discuss the relationships between the classes we have defined above in our LinkedIn system.

Association#

The class diagram has the following association relationships:

• The User class has a one-way association with the following:

  • Itself

  • The CompanyPage, Group, Job, Post, Comment, Message, and ConnectionInvitation classes

  • The Search interface

• The Notification class has a one-way association with the Message, Post, Comment, ConnectionInvitation, and Recommendation classes.

Composition#

The class diagram has the following composition relationships:

• The Person class is composed of the Account class.

• The User class is composed of the Profile class.

• The Profile class is composed of Experience, Education, Skill, Achievement, Recommendation, and Analytics classes.

• The Post class is composed of the Comment class.

• The CompanyPage class is composed of the Job class.

Inheritance#

The following classes demonstrate an inheritance relationship:

• Both the Admin and User classes extend the Person class.

Note: We have already discussed the inheritance relationship between classes in the component section above one by one.

Class diagram of LinkedIn#

Here’s the complete class diagram for LinkedIn:

Design pattern#

We know that LinkedIn allows its users to follow company pages and join a group. By default, when a user follows or joins a page or group, they get notified of any new posts. To effectively map this behavior in our design, we can use the Observer design pattern.

All members of the page or group are set as subscribers, by default, on LinkedIn. Whenever there is a new activity, the system notifies the subscribers. The members also have the option to opt out of these notifications and to remove themselves from the subscriber list.

AI-powered trainer#

At this stage, everything should be clear. If you encounter any confusion or ambiguity, feel free to utilize the interactive AI-enabled widget below to seek clarification. This tool is designed to assist you in strengthening your understanding of the concepts.

We have completed the class diagram of LinkedIn according to the requirements. Now, let’s design the sequence diagram of LinkedIn in the next lesson.