State Vector

We assume a piece of code acts on a finite set of variables $x_1, x_2,...,x_n$ (which may be numeric, Boolean, etc). We call ( $x_1, x_2,...,x_n$) the Program State: it is transformed (many times usually) as the program runs. The $x_i$ represent all variables used in the program.

Suppose $x_i$ takes values from the dataset $X_i$, so the state is a ``vector'' in $X_1 \;$   x$\; X_2 \;$   x$\; ... \; X_n$.