The right derivation operator \$$g: 2^Y \rightarrow 2^X\$$ is defined similarly.

First let \$$g_1: Y \rightarrow 2^X\$$ be the function sending an attribute \$$a \in Y\$$ to the set of objects which have that attribute, i.e.,

\$g_1(a) = \lbrace o \in X\ |\ (o,a) \in K \rbrace \$

Then define the right derivation operator \$$g: 2^Y \rightarrow 2^X\$$ by

\$g(y) = \bigcap_{a \in y} g_1(a)\$

which is equivalent to

> let \$$g(y)\$$ be the objects which have every attribute in \$$y\$$.