An Entity Identifier in OutSystems can ....

An Entity Identifier in OutSystems is designed to uniquely identify each record within an entity. This identifier can consist of a single attribute or a combination of attributes, but it is optimal to keep it as a single attribute for simplicity and efficiency in database operations.

When it comes to practical usage, having a single attribute as the Entity Identifier makes operations like searching, updating, and referencing records straightforward. Using composite keys (multiple attributes as the identifier) can complicate queries and data manipulation, leading to performance issues and increased difficulty in maintaining data integrity.

While other choices touch upon different aspects of how identifiers might be configured or created in OutSystems, the ability for an identifier to be a single attribute is a foundational principle of how they function in relational database structures.