Developing a Conceptual Model › Identifying Relations › Data Relationship Connections

Data Relationship Connections

In your data model, a relationship establishes a connection between one entity and another or between an entity and an attribute. In the database, a relationship links a file to a file, or a file to a field (of the file).

You can identify and categorize relationship types by studying the connection to see whether it falls into the following categories, asking yourself questions such as:

Optional—Is the connection mandatory or optional?

• Does an order require a customer?
• Does a product require a description?
• Does a product require a price?

Cardinality—Is the connection a one-to-one, one-to-many, or many-to-many?

• How many customers can be on a single order?
• How many orders can a customer place?
• How many prices are there for a product?
• How many addresses can a customer have?

Involution—Does the connection exist between two different entities or from the same entity to itself?

• Are components a product, or are they themselves products in their own right?
• Is a manager an employee or is there a separate entity of just managers?

If Manager is an employee, then the relation "Employee Works for Manager" connects to the same entity. This is called involution.

By answering those questions and using an ERD, you will be able to determine the relation types of your data.

All relationships in CA 2E data model descriptions are mandatory. You can make relationships optional at the process level.