Type Inference in the Polymorphic Relational Algebra

We give a polymorphic account of the relational algebra. We introduce a formalism of \type formulas" speci cally tuned for relational algebra expressions, and present an algorithm that computes the \principal" type for a given expression. The principal type of an expression is a formula that species, in a clear and concise manner, all assignments of types (sets of attributes) to relation names, under which a given relational algebra expression is well-typed, as well as the output type that expression will have under each of these assignments. Topics discussed include complexity, the relationship with monadic logic, and polymorphic expressive power.

• Type: Conference
• Year: 1999
• Where: PODS
• Authors: Jan Van den Bussche, Emmanuel Waller
• Keywords: Database, PODS 1999, Polymorphic Account, Relational Algebra, Relational Algebra Expression