\[\begin{array}{l|ll}
  \text{set of}\qquad&\text{representation
by}\qquad&\text{representation by}\\
  \text{states} & \text{boolean values} & \text{boolean function}
\\\hline
  \emptyset &       & 0\\
  \set{s_0} & (1,0) & x_1\cdot\bar{x_2}\\
  \set{s_1} & (0,1) & \bar{x_1}\cdot x_2\\
  \set{s_2} & (0,0) & \bar{x_1}\cdot\bar{x_2}\\
  \set{s_0,s_1} & (1,0),\,(0,1) & x_1\cdot\bar{x_2}+\bar{x_1}\cdot x_2\\

  \set{s_0,s_2} & (1,0),\,(0,0) &
x_1\cdot\bar{x_2}+\bar{x_1}\cdot\bar{x_2}\\
  \set{s_1,s_2} & (0,1),\,(0,0) & \bar{x_1}\cdot x_2 +
\bar{x_1}\cdot\bar{x_2}\\
  S             & (1,0),\,(0,1),\,(0,0) &
x_1\cdot\bar{x_2}+\bar{x_1}\cdot x_2+\bar{x_1}\cdot\bar{x_2}\\
\end{array}\]