relationdepends

Relationdepends is a term encountered in theoretical discussions of relational models to describe a dependency between two relations in which the content of one relation is conditioned by or derived from the content of another. It is not a standard term in mainstream database theory, and its precise meaning can vary between sources.

In a typical interpretation, let R and S be relations over domains. R depends on S if every tuple r in R is associated with at least one tuple s in S via a predicate linking their fields; equivalently, R contains exactly that subset of tuples that are connected to S by the linking condition. This captures a cross-relational constraint that goes beyond simple functional or inclusion dependencies.

Example: suppose S(PersonID, Name) lists registered users, and R(Phone, PersonID) lists phone numbers. Under a relationdepends interpretation with a linking predicate P(PersonID), a tuple (Phone, PersonID) is allowed in R only when there exists a matching s in S with the same PersonID; thus R depends on S.

Applications of relationdepends include deductive databases, view maintenance, data integration, and constraint programming to express indirect or derived dependencies across relations. The notion can also inform reasoning about provenance and data completeness, since the validity of R is tied to S. While useful conceptually, relationdepends remains a nonstandard term and its exact formulation is problem- and text-specific, often treated as a generalization of cross-relational constraints rather than a single canonical operator. Related ideas include functional dependencies, inclusion dependencies, join dependencies, and view dependencies.