1. Describe the purpose of ERD. 2. Assume that teachers are assigned to a class schedule in your school . The Teacher entity has teacher id, name, sex, and specialization attributes . The Schedule entity has schedule __ id, room, period, and section attributes. Con- struct an ERD based on the description given. Activity 3.4

1. **Purpose of ERD (Entity-Relationship Diagram):**<br /><br /> An Entity-Relationship Diagram (ERD) is a visual representation of the data and relationships within a database system. The primary purposes of an ERD are:<br /><br /> - **Visualization:** It provides a clear and organized way to visualize the structure of a database, showing entities, attributes, and the relationships between them.<br /> <br /> - **Design:** ERDs are used in the design phase of database development to ensure that all necessary data elements and their relationships are captured accurately.<br /> <br /> - **Communication:** They serve as a communication tool among stakeholders, such as database designers, developers, and business analysts, to discuss and refine database requirements.<br /> <br /> - **Documentation:** ERDs act as documentation for the database structure, which can be referred to during maintenance and future development.<br /><br />2. **Constructing an ERD:**<br /><br /> Based on the description provided, we have two main entities: `Teacher` and `Schedule`. Here’s how you can construct an ERD:<br /><br /> - **Entities:**<br /> - **Teacher**<br /> - Attributes: <br /> - Teacher ID (Primary Key)<br /> - Name<br /> - Sex<br /> - Specialization<br /><br /> - **Schedule**<br /> - Attributes:<br /> - Schedule ID (Primary Key)<br /> - Room<br /> - Period<br /> - Section<br /><br /> - **Relationships:**<br /> - A relationship exists between `Teacher` and `Schedule`, indicating that teachers are assigned to class schedules. This relationship can be represented as "Assigned To" or similar.<br /><br /> - **Cardinality:**<br /> - Depending on the rules of your school, each teacher might be assigned to multiple schedules, and each schedule might have multiple teachers. However, if each schedule is uniquely assigned to one teacher, this would be a one-to-many relationship from `Teacher` to `Schedule`.<br /><br />Here is a simple textual representation of the ERD:<br /><br />```<br />[Teacher] --< Assigned To >-- [Schedule]<br /><br />[Teacher]<br />- Teacher ID (PK)<br />- Name<br />- Sex<br />- Specialization<br /><br />[Schedule]<br />- Schedule ID (PK)<br />- Room<br />- Period<br />- Section<br />```<br /><br />In a graphical ERD, you would use rectangles to represent entities, ovals for attributes, diamonds for relationships, and lines to connect these components, with appropriate cardinality indicators (e.g., 1:1, 1:N, N:M) to show the nature of the relationships.