Question

Draw an EERD for the following situation. Students are required to turn in assignments. Attributes of STUDENT include StudentID (identifier), Name, and Major. Attributes of ASSIGNMENT include AssignmentNo (identifier) and DueDate. The grade obtained by each student for each assignment is recorded. Assignments may be either modeling or computer assignments. Computer assignments have an additional attribute, PlatformUsed. Modeling assignments are based on cases. A case may be used in one or more modeling assignments, and a given modeling assignment is associated with exactly a case. Attributes of CASE include CaseNo (identifier) and Author.

Answer 1

Please find below the steps to create EERD for the given system description:

Step 1: List entities:

Below are the main and sub entities to be available in the system:

1. STUDENT: Entity to store student details

2. ASSIGNMENT: Entity to store assignment details

3. MODELING_ASSIGNMENT: Sub-entity of ASSIGNMENT entity

4. COMPUTER_ASSIGNMENT: Sub-entity of ASSIGNMENT entity

5. CASE: Entity to store the case details for modelling assignment

Step 2: List relationship:

1. ASSIGNMENT can be either MODELING_ASSIGNMENT or COMPUTER_ASSIGNMENT. This is an IS-A relationship with disjoint relationship.

2. ASSIGNMENT is submitted by one STUDENT, it is a M:1 relationship based on assumption that a STUDENT can submit many assignments.

3. MODELING_ASSIGNMENT has one CASE and a CASE may have many MODELING_ASSIGNMENT. It is a M:1 relationship.

Step 3: Add attributes to the entities:

STUDENT(StudentID , Name, Major)

ASSIGNMENT(Assignment_ID, DueDate, ObtainedGrade)

COMPUTER_ASSIGNMENT(PlatformUsed)

CASE(CaseNo , Author)

Step 4: Create EERD:

Step 5: EERD Symbols: