ESPRIT Project 322, "CAD Interfaces", has been established to define the most important interfaces in CAD/CAM systems for data exchange, data base, finite element analysis, experimental analysis, and advanced modeling. The definitions of these interfaces are being elaborated in harmony with international standardization efforts in this field. One principal goal of the project is to develop techniques for the exchange of CAD information between CAD systems, and from the CAD domain to CAA (Computer Aided Analysis) and CAM (Computer Aided Manufacturing). This volume presents a proposal for a neutral file format for CAD data: curves, surfaces, and solids. The specification is based on a reference schema for CAD data bases and is defined informally with respect to its semantics and formally with respect to its syntax. This volume is a revised edition of "Specification of a CAD*I Neutral File for Solids" Version 3.2. The revision reflects the enhancements which result from the implementation of communication processors in eight different CAD systems and from the practical exchange of solid models between these systems. Due to the close interaction between the CAD*I project and the coming-up international standard STEP this specification also serves as an introduction to the geometry model that will be included in the future international standard.
