= Conceptual Design – ER Diagram and Data Requirements =

== ER Diagram ==
[[Image(Er,OLPMS.jpg, 1200px)]]
 


== Data Requirements ==

=== Entities ===

* **User: Entity representing all users who access the platform (students / learners).**
  * User_ID – INT (PRIMARY KEY)
  * First_Name – VARCHAR
  * Last_Name – VARCHAR
  * Email – VARCHAR(unique)
  * Password – VARCHAR

* **Administrator: Entity representing instructors who create and manage educational content.**
  * Admin_ID – INT (PRIMARY KEY)
  * Admin_Level – VARCHAR

* **Instructor: Entity representing instructors who upload and manage course materials.**
  * Instructor_ID – INT (PRIMARY KEY)
  * BIO – VARCHAR
  * Ekspertise – VARCHAR
  
* **Course: Entity representing the courses offered on the platform.**
  * Course_id – INT (PRIMARY KEY)
  * Name – VARCHAR
  * Price – Decimal
  * status – VARCHAR

* **Enrollment: Entity representing the enrollment of a user in a course.**
  * Enrollment_id – INT (PRIMARY KEY)
  * Enroll_date – DATE
  * Completion_Status – VARCHAR
  * Progress_percentage – INT

* **Payment: Entity representing financial transactions.**
  * Payment_ID – PRIMARY KEY
  * Amount – DECIMAL

* **SubscriptionPlan: Entity representing available subscription plans.**
  * Plan_ID – INT (PRIMARY KEY)
  * Name – VARCHAR
  * Price – DECIMAL
  * Duration_months – INT
  * Description – VARCHAR
  * Access_type – VARCHAR

* **Certificate: Entity representing certificates issued after course completion.**
  * Certificate_id – INT (PRIMARY KEY)
  * Issue_date – DATE
  * Certificate_code – VARCHAR
  * Status – VARCHAR

* **UserSubscription: Entity representing active subscriptions of users.**
  * Subscription_ID – INT (PRIMARY KEY)
  * Start_date – DATE
  * End_date – DATE
  * Status – VARCHAR

* **SupportTicket: Entity representing user support requests.**
  * Ticket_ID – INT (PRIMARY KEY)
  * Subject – VARCHAR
  * Description – VARCHAR
  * Status – VARCHAR
  * Created_at – DATE

* **Category: Entity representing course classification.**
  * Category_ID – INT (PRIMARY KEY)
  * Name – VARCHAR
  * Description – VARCHAR

* **Module: Entity representing logical subdivisions of a course.**
  * Мodule_id – INT (PRIMARY KEY)
  * Тitle – VARCHAR
  * Description – VARCHAR
  
* **Lesson: Entity representing individual learning units.**
  * Lesson_ID – INT (PRIMARY KEY)
  * Тitle – VARCHAR
  * Material – VARCHAR
 
* **Quiz: Entity representing assessments associated with lessons.**
  *  Quiz_ID – INT (PRIMARY KEY)
  * Total_points – INT
  * Passing_score – INT

=== Relationships ===

* '''Pays''' - 1:N between User and Payment. One user can make multiple payments, Each payment is associated with exactly one user.

 * '''Has''' - 1:N relationship between User and UserSubscription. Each user subscription belongs to exactly one user.

 * '''Has''' - N:1 relationship between UserSubscription and SubscriptionPlan. Each user subscription is based on exactly one subscription plan, One subscription plan can be associated with many user subscriptions.

 * '''Subscription''' - 1:N relationship between UserSubscription and Payment. One user subscription can be paid through one or multiple payments, Each payment is associated with exactly one user subscription.

 * '''Creates''' - 1:N relationship between User and SupportTicket. One user can create multiple support tickets, Each support ticket is created by exactly one user.

 * '''Manages''' - 1:N relationship between Administrator and SupportTicket. One administrator can manage multiple support tickets, Each support ticket is managed by exactly one administrator.

 * '''Manages''' - 1:N relationship between Administrator and Course. One administrator can manage multiple courses, Each course is managed by exactly one administrator.

 * '''Uploads and manages''' - 1:N relationship between Instructor and Course. One instructor can upload and manage multiple courses, Each course is uploaded and managed by exactly one instructor.

 * '''Enrolls''' - 1:N relationship between User and Enrollment. One user can have multiple enrollments, Each enrollment is associated with exactly one user.

 * '''Enrolls ''' - N:1 relationship between Enrollment and Course. Each enrollment is associated with exactly one course, One course can have multiple enrollments.

 * '''Receives''' - 1:1 relationship between Enrollment and Certificate. Each enrollment can lead to exactly one certificate, Each certificate is issued for exactly one enrollment.

 * '''Creates ''' - 1:N relationship between Course and Module. One course can create and contain multiple modules, Each module belongs to exactly one course.

 * '''BelongsTo''' - N:1 relationship between Course and Category. Each course belongs to exactly one category, One category can include multiple courses.

 * '''Has''' - 1:N relationship between Module and Lesson. One module can contain multiple lessons, Each lesson belongs to exactly one module.

 * '''Has''' - 1:1 relationship between Lesson and Quiz. Each lesson has exactly one quiz, Each quiz is associated with exactly one lesson.