An arc tube array-type display device includes an arc tube array, a supporting member, a plurality of display electrodes, a plurality of scan electrodes, and a plurality of address electrodes. Customer activity to an existing service center is monitored, providing customer model, which includes a collection of customer tasks. During the plasma processing, the plasma passes through the liner without affecting the liner. In an apparatus according to the invention, the optical power of the lens systems is altered by altering the energy with which the beam traverses the lens systems. The classification system can be applied to an email filtering system for filtering spam email.