Developing an Entity Relationship Diagram (ERD)

This week, you need to develop an Entity Relationship Diagram (ERD) for the database that models your chosen domain. This assignment consists of three steps:

1. Identify entities;
2. find relationships; and
3. Draw the ERD blueprint.

Step 1: Identify Entities

Identify the entities. These are typically the nouns and noun-phrases in the descriptive data produced in your analysis. Do not include entities that are irrelevant to your domain.

For example, in a college database project, the entity candidates are departments, chair, professor, course, and course section. Since there is only one instance of the university, we exclude it from our consideration for now.

Step 2: Find Relationships

Discover the semantic relationships between entities. In English, the verbs connect the nouns. Not all relationships are this blatant; you may have to discover some on your own. The easiest way to see all the possible relationships is to build a table with the entities across the columns, and down the rows. Then, fill in cells to indicate where relationships exist between the entities.

Step 3: Draw the ERD Blueprint

Draw the entities and relationships you have discovered. View the example of a college database project ERD blueprint

To create your ERD, the domain (or subset of a domain) that you chose for your project should include the following characteristics:

• Size. An appropriately sized domain results in a database with about a dozen entries (more or less).
• Relationship. The entities comprising your domain should be interrelated.
• Functionality. The scope of the diagram shows the operations or functions that the database project addresses. It also identifies the functions that fall outside of the application.
• Description. Define the data requirement of your entities. For example:
• Student Entity: Members of the public who register and pay for courses are considered students. The data stored on each student includes student number, name, address, email address, previous classes, and experience. Also stored is the date for registration and the classes they are registered in. The student number is unique for each student.
• Course Entity: The school offers a variety of Online design courses through its website (these are considered course, not the on-location seminars). The data stored on each course includes the course number, the name of the course, the course description, and prerequisites (if any). The course number is unique, etc.