What is the main purpose of an Entity-Relationship Diagram (ERD)?

The primary purpose of an Entity-Relationship Diagram (ERD) is to illustrate the structure of a database and the relationships between different entities. In the context of system analysis and design, an ERD visually represents how entities (such as tables in a relational database) are interconnected. It shows the attributes of these entities and the types of relationships (like one-to-one, one-to-many, or many-to-many) that exist between them.

By representing this information clearly, ERDs help designers and stakeholders understand data requirements and how data will be organized within the system. This visualization is crucial for database design, enabling efficient data management and the clarity necessary for developers and users alike.

The other options—outlining user interactions, depicting system workflows, and establishing security protocols—address different aspects of system design and analysis, but they do not capture the specific intent of an ERD, which is focused solely on data structure and relationships.