Materialized Views Declarative Databases Deductive databases are relational databases extended with the facility to define views recursively .
Deductive databases allow the specification of such views declaratively.
Such research involves defining the semantics of view definitions that use these features, and deriving optimization techniques for this more general class of view definitions. A different example of my work in this area is in defining an extended relational algebra where relations may store relation names as attribute values. More recent work has focused on defining virtual columns of existing tables in a view-like fashion.