The Structure and Operation of a Relational Database System in a Cell-Oriented Integrated Circuit Design System

An important use for a database management system is in the storage and handling of information for engineering design, particularly integrated circuit design. However, most discussions on this topic have concentrated on the layout of shapes necessary to form the various circuit elements, or connections between user-defined cells. Equally important, but often disregarded, is the necessity to support other design tools in addition to graphics for circuit layout. These include simulators and automatic layout programs that take a description of a circuit at one level and convert it to a lower level. In addition, if cells are part of a library defined and maintained by others, operations must be included to handle the maintenance of generations or versions of a cell design. These aspects of a database management system for engineering design are discussed in light of the tools being developed at the University of Utah and an extended version of System R, developed at the IBM San Jose Research Laboratory. The Utah approach emphasizes the use of previously designed and tested cells, with interconnects at fixed locations, placed on a grid. Because it is unlikely that the designers of circuits designed all (or any) of the cells used in their circuits, special database management operations are necessary to assure that a consistent, working circuit results.