Which of the following mappings between OutSystems and the Database is NOT correct?

In the context of OutSystems and its mapping to a relational database, a reference attribute typically does not correspond to a primary key directly. Instead, reference attributes are used to create relationships between different entities by linking to the primary key of another entity. Thus, saying that a reference attribute is synonymous with a primary key is misleading.

Entities in OutSystems are indeed represented as tables in the database, and attributes correlate directly to columns within those tables. Moreover, the mapping of indexes in OutSystems to database indexes is also accurate, as indexes serve the purpose of optimizing query performance in both the OutSystems environment and relational databases.

In summary, the assertion about reference attributes being equivalent to primary keys is where the misunderstanding lies, as it overlooks the relational nature of how these components interact within a data model.