Final answer:
The first step in building an entity-relationship diagram (ERD) is identifying the entities and their relationships, which involves analyzing the problem and determining the interconnections between pieces of information to be stored.
Step-by-step explanation:
The first step in building an entity-relationship diagram (ERD) is identifying the entities and their relationships. This foundational step is crucial as it sets the stage for all other components of the ERD. You start by analyzing the problem domain to reveal what information is to be stored and how these pieces of information are connected. This process may include identifying real-world subjects that the database will represent, which are referred to as entities, and understanding the nature of the interactions between these entities, which form the relationships. Only after establishing a clear picture of entities and relationships should the designer proceed to create attributes for each entity, define the cardinality and participation constraints, and ultimately drawing the diagram to visualize the structure.