Assignment 4: Erduse The Following Business Rules To Create
Assignment 4 Erduse The Following Business Rules To Create A Crows F
Assignment 4: ERD Use the following business rules to create a Crow’s Foot ERD. Write all appropriate connectivity and cardinalities in the ERD.
- A department employs many employees, but each employee is employed by only one department.
- Some employees, known as “rovers,” are not assigned to any department.
- A division operates many departments, but each department is operated by only one division.
- An employee may be assigned many projects, and a project may have many employees assigned to it.
- A project must have at least one employee assigned to it.
- One of the employees manages each department, and each department is managed by only one employee.
- One of the employees runs each division, and each division is run by only one employee.
Paper For Above instruction
Introduction
The development of an Entity-Relationship Diagram (ERD) is a fundamental step in database design, representing entities and their relationships within an organization. Based on the provided business rules, this paper constructs a comprehensive Crow’s Foot ERD, detailing the entities, their attributes, and the relationships, including cardinalities and connectivity types.
Entities and Attributes
The core entities derived from the business rules include:
- Department: Attributes include department_id, name, and potentially other descriptive attributes.
- Employee: Attributes include employee_id, name, role, and potentially other specifics.
- Division: Attributes involve division_id, division_name, etc.
- Project: Attributes include project_id, project_name, and relevant project data.
Each entity is characterized by a primary key; for example, employee_id uniquely identifies each employee.
Relationships and Cardinalities
The ERD must accurately depict the relationships and their cardinalities:
1. Department to Employee:
- A department employs many employees.
- Each employee is employed by only one department.
- This is a one-to-many (1:N) relationship from Department to Employee.
2. Employee to Department (Manager relationship):
- Each department is managed by one employee.
- An employee can manage only one department.
- This is a one-to-one (1:1) relationship, but since both roles involve employees and departments, it can be modeled as a one-to-one self-relationship with roles designated as manager.
3. Employee to Project:
- Many employees can work on many projects.
- Each project must have at least one employee assigned.
- This is a many-to-many (M:N) relationship, resolved with an associative entity, for example, "Assignment".
4. Division to Department:
- A division operates many departments.
- Each department belongs to one division.
- This is a one-to-many (1:N) relationship from Division to Department.
5. Employee to Division (Runner relationship):
- An employee runs a division.
- Each division is run by only one employee.
- Similar to the manager relationship, a one-to-one (1:1) relationship is appropriate here.
Constructing the ERD
Using Crow’s Foot notation:
- Entities are represented as rectangles.
- Relationships are represented as diamonds or lines connecting entities.
- Cardinalities are shown with symbols: "1" for one, "M" for many, "0..1" for optional one, etc.
For example:
- The "Department" entity connects to "Employee" with a line indicating "employs" (1:N), with the "Employee" side annotated with "employed by" optional, to represent "rovers."
- The "Division" connects to "Department" with a 1:N relationship labeled "operates."
- The "Employee" and "Project" are connected through "Assignment" with a M:N relationship, where "Assignment" records which employees are assigned to which projects.
- The "Department" connects to "Employee" with a 1:1 relationship (managed by), and similarly, "Division" connects to "Employee" (run by).
The ERD thus visualizes the intricate organizational structure, ensuring all business rules regarding optional and mandatory relationships are accurately represented.
Conclusion
The constructed Crow’s Foot ERD encapsulates the organizational entities and their interrelations per the specified business rules. Proper representation of optional relationships (rovers’ acceptance), enforced cardinalities (e.g., projects having at least one employee), and dual roles of employees (manager and runner) ensures a comprehensive and functional database design framework. This ERD provides a clear blueprint for implementing a robust database aligned with business operations.
References
- Elmasri, R., & Navathe, S. B. (2016). Fundamentals of Database Systems (7th ed.). Pearson.
- Ceri, S., & Pelagatti, G. (1984). atabases and Data Integrity. McGraw-Hill.