By using business keys to map objects, you can apply object-oriented programming to available relational database tables in existing applications. However, you can create a new object model that is based on database tables with semantic keys. In these cases, the Class Builder generates a key attribute in the persistent class for every primary key field in the database table. Mapping by business key involves mapping the key attributes to the primary key of an existing database table. At runtime, the Persistence Service links each managed object of the persistent class to the table entry whose key field values match the object’s key attributes.

You cannot change the key attributes of a persistent class. The Mapping Assistant only generates GET methods and no SET methods. The key attributes form the business key of a persistent class.

Thus a business key is a semantic key that is visible externally.