Abstract: Disclosed is a multi-dimensional selectivity estimation method using compressed histogram information which the database query optimizer in a database management system uses to find the most efficient execution plan among all possible plans. The method includes the several steps to generate a large number of small-sized multi-dimensional histogram buckets, sampling DCT coefficients which have high values with high probability, compressing information from the multi-dimensional histogram buckets using a multi-dimensional discrete cosine transform(DCT) and storing compressed information, and estimating the query selectivity by using compressed and stored histogram information as the statistics.

Abstract: A process of manufacturing a roll punch used for forming the partition walls on the rear panel of a PDP is disclosed. In the process of this invention, a forming roll is primarily coated with a mask on its external surface. The mask is, thereafter, partially removed from the forming roll, thus forming a plurality of regularly spaced mask-free parts on the forming roll. The forming roll is, thereafter, etched at the mask-free parts using ultrasonic waves within an etching tank, and so a desired roll punch having partition wall forming grooves is produced. This manufacturing process enlarges the width of the lands between the forming grooves of the roll punch, thus allowing an easy arrangement of address electrodes on the rear panel of a PDP. It is also possible to produce a desired highly precise roll punch by properly adjusting the intervals between the mask-free parts of the forming roll.

Abstract: A device for forming partition walls of a plasma display panel is disclosed. This device has a lower plate used for seating the base panel of the plasma display panel thereon, with a partition wall sheet of a predetermined thickness formed on the base panel and a plurality of electrodes arranged on the base panel. A punch, having a plurality of partition wall forming grooves and a plurality of lands formed between the partition wall forming grooves. An electrode holding groove or inclined surface is formed on each of the lands and is used for preventing the electrodes from being undesirably moved during a partition wall forming process. An upper plate is positioned above the punch so as to hold the punch and to move the punch in a vertical direction within a predetermined range.