Comprehensive and Detailed Explanation From Exact Extract:

The purpose of a foreign key relationship in the ABAP Dictionary is to ensure the integrity of data between the related database tables. This relationship checks that values entered in the foreign key field exist in the check table, thereby preventing invalid or orphaned entries.

While foreign key relationships do not automatically enforce constraints at the database level, they are used for enforcing referential integrity at the application layer and play a key role in:

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Validation checks during data modification

Ensuring consistency of master and transaction data

This aligns with the standard ABAP development model, where the application layer (not the database) handles logical consistency using metadata from the ABAP Dictionary.