Relational databases "do not allow referential integrity constraints to span databases". The recast databases support commonality constraints where referential integrity may be enforced between databases. Jet enforces entity integrity and referential integrity. It supports all combinations of UML multiplicity and enforces referential integrity. It has two types&colon; referential and typological intertextuality. Their works also imply symbols existing outside of any referential context. Some programming languages provide means to guarantee referential transparency. Some scenarios can cause Referential integrity problems. Dynamic scoping also voids all the benefits of referential transparency. CODASYL supports insertion and retention that are not captured by referential integrity alone. It also fails to support referential integrity. Head turning and gaze are other gazes that infants view as referential cues. His name is an acronym for Referential Universal Digital Indexer. This type of behavior is common on web portals and referential content sites.