P. Hall, J. Owlett, and S. J. P. Todd. Relations and Entities . Moreover , as we will see in section 7, it helps us to get the problems with oid s into focus. A surrogate is an identifier assigned to the representation of an object by the database system itself, when that representation of the object is entered in the database. Relations and entities .
Surrogates are by definition time invariant.
The opposite of time invariant is time varying. In the schema R above, the courses taken by a student varies over time, and the attribute Course is time varying. G. M. Nijssen. A description of the time domains is given shortly. Surrogates are system generated unique internal identifiers.