What step is necessary for a 1-to-many relationship between a Master Entity A and a Detailed Entity B?

To establish a 1-to-many relationship between a Master Entity A and a Detailed Entity B, it's essential for Entity B to have a reference attribute that links it back to Entity A. This reference acts as a foreign key and indicates that multiple instances of Entity B are associated with a single instance of Entity A.

By including this reference attribute in Entity B, you enable the underlying data model to maintain the necessary linkage, allowing for efficient data retrieval and management. This is crucial when generating queries that involve both entities, as it ensures that you can easily access all the detailed records associated with a specific master record.

In contrast, the other choices either misrepresent the structure required for a 1-to-many relationship or introduce unnecessary complexity that doesn't align with the requirements. For example, creating a new entity with two reference attributes or setting an identifier in the reverse direction does not achieve the intended relationship structure. Ultimately, having Entity B hold a reference to Entity A ensures clarity in the relationships between your data entities, which is foundational for database integrity in OutSystems applications.