The embodiments of the invention generally relate to a novel magnet arrangement to further enhance the performance of the array. The seat back unit includes a tiltable seat back erected on a floor surface; a seat back locking mechanism for locking a tilt of the seat back; and a rocking member rocking in cooperation with a tilting operation of the seat back after unlocking the seat back locking mechanism. Classifiers automatically classify the search content by identifying the content corresponding with associated facets.