$`\newcommand{\mrm}[1]{\mathrm{#1} }
\newcommand{\mvto}{ \twoheadrightarrow }
\newcommand{\Iff}{\Leftrightarrow}
\newcommand{\Imp}{\Rightarrow}
`$
関数従属性
$`\mrm{FD}(X\to Y)(R) :\Iff \\
\quad \forall t_1, t_1 \in R. \,
t_1[X] = t_2[X] \Imp t_1[Y] = t_2[Y]
`$
言い換えると：
$`\mrm{FD}(X\to Y)(R) :\Iff \\
\quad \vec{R}:R[X] \to R[Y] \text{ is-a function}
`$
多値従属性
$`\text{When }X\cap Y = \emptyset\\
\mrm{MVD}(X \mvto Y)(R) :\Iff\\
\quad \forall t_1, t_2 \in R.\,
t_1[XY] = t_2[XY] \Imp\\
\qquad \exists t \in R. t[XY] = t_1[XY] \land t[X(R - XY)] = t_2[X(R - XY)]
`$
言い換えると：
$`\text{Whe }X, Y, Z \text{ mutually disjoint}\\
\mrm{MVD}(X \mvto Y)(R) :\Iff\\
\quad \forall t_1, t_2 \in R.
t_1[XY] = t_2[XY] \Imp\\
\qquad \exists t \in R. t[XY] = t_1[XY] \land t[XZ] = t_2[XZ]
`$
