Lightweight Formats for Product Model Data Exchange and Preservation Alexander Ball (1) , Lian Ding (2) , Manjula Patel (1) (1) UKOLN, University of Bath Claverton Down, Bath BA2 7AY, United Kingdom EMail: a.ball@ukoln.ac.uk EMail: m.patel@ukoln.ac.uk (2) IdMRC, University of Bath Claverton Down, Bath BA2 7AY, United Kingdom EMail: ld218@bath.ac.uk ABSTRACT The designs for engineered products are increasingly defined not by technical drawings but by three-dimensional Computer Aided Design (CAD) models. With rapid turnover of computer hardware and CAD software, these models are in danger of becoming unreadable long before their usefulness has ended. One possible approach is to migrate the models into lightweight formats that are easier to preserve and from which it will be easier to recover information in the future. Such formats also have benefits for design collaboration and dissemination of product model information. Selecting the right lightweight format to use remains a problem, but considering matters of model fidelity, metadata support, security features, file size, software support, and openness, the difference between the formats is not as significant as their common advantages over full-featured, complex models. Product model data, lightweight representations, digital curation INTRODUCTION Since the turn of the millennium, the engineering sector has been undergoing a paradigm shift in the way that products are designed and manufactured or constructed. Formerly, Computer Aided Design (CAD) tools were used simply to generate blueprints and other two dimensional technical drawings, so that the official description of the product could be set down on paper. Increasingly, though, three-dimensional (3D) CAD models are being integrated into the engineering workflow, being used as the basis of finite element analysis, stereolithographic prototyping, numerical control part programmes and product inspections, for example. Thus the 3D CAD models are taking over as the official record of a product’s design. Long-term users of engineering product data — including maintenance engineers, accident investigators and designers working on similar products — face a significant challenge due to the ephemeral nature of CAD file formats and the applications that work with them. One way of dealing with this is to migrate the CAD information as soon as possible into lightweight formats that are easier to preserve and from which it will be easier to recover information in the future. This approach may also have immediate benefits for collaboration and the dissemination of product model information. The complexity of full-featured CAD formats means that the file sizes of the models can be too large for comfortable transmission over the Internet, making distributed design work much harder. Lightweight representations, by contrast, can have much smaller file sizes. Furthermore, lightweight for- mats often have free viewers, enabling models to be disseminated, accessed and re-used (for example, in marketing documents) much more widely. Probably because of this, lightweight formats typically also have some intellectual property (IP) protection mechanism, whether by approximating the original model 1