TR065: A Framework for Change Management in a Design Database

The complexity of many engineering designs is now so great that it is impossible for one engineer to complete a design alone. Instead, a team of engineers work collaboratively to achieve the design. This is known as concurrent design. Despite evolution of computer-aided design (CAD) tools toward integrated use of a design database, tools continue to assume that they will operate in isolation from one another and will take turns accessing and manipulating design data. The result is a tool-centric approach that makes close cooperation among a team of design engineers impossible.

This thesis argues that a tool-centric approach is unsuitable in a design environment for concurrent design, which requires a new design-centric approach that does permit close cooperation, and that existing tools and design databases cannot offer that new approach. As a framework for the design-centric approach, this thesis presents the Change Manager, which is a collection of software modules that are distributed among CAD tools and the design database. The Change Manager augments the functionality of tools and the database by serving as an intermediary between application code in a tool, and design data in the database.

The Change Manager offers a flexible model of concurrency control without the need for exclusive locks, and also provides support for close cooperation of engineers and their tools. The collaboration can be informal—directly among the engineers—as well as formal—computer-mediated. The Change Manager provides mechanism and protocol, but does not enforce policy. This thesis describes the architecture and operation of the Change Manager, explains how it supports a design-centric approach, and presents invariants that its operation guarantees.