Both CAD and VLSI are data-intensive. One of the key ingredients in a design project is the ability to keep track of various changes that evolve. The software engineering approach to this task is called version modeling. The author presents a unified view of several mechanisms available for version modeling. No new version models are introduced.

This survey paper proceeds methodically. A version is defined as “a snapshot of a design object at a point in time.” The paper then details the various technical issues involved with version modeling. Some of these are inheritance, currency, dynamic configuration, and workspace management. The significance here is that these concepts provide a natural follow-up to the object-oriented approach. The paper also mentions the traditional relational model and the entity-relation model. Section 3 provides succinct summaries of 14 well-known models. The paper concludes with a section that provides the grand unification that was set out as a goal at the beginning. The paper is easily readable. The bibliography contains over 30 references. The paper should interest people working in databases and software engineering.