Towards a Curation and Preservation Architecture for CAD Engineering Models

For many decades, computer-aided design (CAD) packages have played an important part in the design of product models within the engineering domain. Within the last ten years, however, the increasing complexity of CAD models and their tighter integration into the workflow of engineering enterprises has led to their becoming the definitive expression of a design. At the same time, a paradigm shift has been emerging whereby manufacturers and construction companies enter into contracts to take responsibility for the whole lifecycle of their products – in effect, to sell their product as a service rather than as an artefact. This makes necessary not only the preservation of the product’s design, but also its continuing intelligibility, adaptability and reusability throughout the product’s lifecycle. The CAD models themselves, though, are typically in closed formats tied to a particular version of an expensive proprietary application prone to rapid obsolescence. While product lifecycle management (PLM) systems deal with some of the issues arising from this, at present it is not possible to implement a comprehensive curation and preservation architecture for CAD models, let alone the other forms of engineering information. In order to fill in some of the gaps in a possible architecture, we have developed two tools to aid in the curation and preservation of CAD models. The first is a preservation planning tool for CAD models: a Registry/Repository of Representation Information for Engineering (RRoRIfE). The tool uses Representation Information, as defined by the Open Archival Information System (OAIS) Reference Model, to advise on suitable strategies for migrating CAD models to archival or exchange formats. The second – Lightweight Models with Multilayered Annotations (LiMMA) – is an architecture for layering non-geometric information on top of a geometric model, regardless of the format used for the geometric model. We envision this architecture being used not only to create flexible, lightweight archival representations of model data, but also to facilitate better information flows between a design team and the rest of the extended enterprise.