Definition


A pair (R, F) of a temporal relation schema R and a set of associated temporal functional dependencies F is in temporal Boyce-Codd normal form (TBCNF) if

∀  X$\displaystyle \;\stackrel{{\mbox{\rm\tiny T}}}{{\rightarrow}}\;$Y  ∈F+  (Y⊆X∨X$\displaystyle \;\stackrel{{\mbox{\rm\tiny T}}}{{\rightarrow}}\;$R)

where F+ denotes the closure of F and X and Y are sets of attributes of R.

Similarly, (R, F) is in temporal third normal form (T3NF) if for all non-trivial temporal functional dependencies X$\;\stackrel{{\mbox{\rm\tiny T}}}{{\rightarrow}}\;$Y in F+, X is a temporal superkey for R or each attribute of Y is part of a minimal temporal key of R.

The definition of temporal fourth normal form (T4NF) is similar to that of TBCNF, but also uses temporal multivalued dependencies.