References and Reference Properties
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References
A reference can be either a human-readable or internal object reference. Human-readable references refer to identifiers used in human communication, such as the unique names of astronomical bodies, the ISBN number of books, or the employee identification numbers of a company. Internal object references refer to the computer memory addresses of OOP objects, providing an efficient mechanism to access objects in the main memory of a computer.
Some languages, like SQL and XML, only support human-readable references—not internal ones. In SQL, human-readable references are called foreign keys. The identifiers that the foreign keys refer to are called primary keys. In XML, human-readable references are called ...