Armstrong's axioms

Armstrong's axioms are a set of axioms (or, more precisely, inference rules) used to infer all the functional dependencies on a relational database. They were developed by William W. Armstrong on his 1974 paper. The axioms are sound in generating only functional dependencies in the closure of a set of functional dependencies (denoted as ) when applied to that set (denoted as ). They are also complete in that repeated application of these rules will generate all functional dependencies in the closure .