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 in his 1974 paper. The axioms are sound in generating only functional dependencies in the closure of a set of functional dependencies (denoted as ${\displaystyle F^{+}}$) when applied to that set (denoted as ${\displaystyle F}$). They are also complete in that repeated application of these rules will generate all functional dependencies in the closure ${\displaystyle F^{+}}$.

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