Referential Integrity in the Context of a Relational Database

While reading SQL and Relational Theory How to Write Accurate SQL Code by C.J. Date I came across the explanation of a term named referential integrity:

"A database satisfies the referential integrity rule if and only if for every tuple containing a reference (i.e., a foreign key value) there exists a referent (i.e., a tuple in the pertinent 'target' relvar with that same value as a value for the pertinent target key). Loosely: If B references A, then A must exist."

C.J. Date

The idea of referential integrity is one that I had intuitively thought about on a more general basis while working with foreign key contstraints in relational database management systems, but had not found a name for.