Declustering has been proposed t,o speed up pa.rallel database machine. However, t,he securit#y requires clustering. In this paper, we use tempora.1 clustering to reconcile the apparent conflict. Aut.oma.ta. theory is applied to high level a.rchitecture design. Based on Petri net theory a da.ta.base ma.chine is proposed. The classical notion of clustering is esknd to tempora.1 dimension and is imported to parallel databa.se syst,ems. The proposed database ma.chine not only has t,he linear speedup, its capability (modeling power) also is increased in the order of magnitude. The computational model (in terms of automa.ta) of the total system is strictly higher than the union of t.1la.t of individua.1 machine. It also efficiently support t,he securit.y.