Xml-based Three-dimensional Cad Model Data Exchange

The Computer-Aided Design technology is being used in the world widely, new application demands, new resolutions, new advanced technologies appear continually. Currently, the main CAD softwares are parametric and feature-based, and the three-dimensional modeling technology is the pivotal technology, the network application is one of the main development directions. The two-dimensional sketch consists of basic geometry items; the different expressions of the same geometry item must be interchangeable on the basis of mathematics and geometry, which is the theoretic basis of the interchange of the two-dimensional sketches between different CAD softwares. The feature, three-dimensional entity, consists of basic three-dimensional entity, which can be created by two-dimensional sketch's movement in the three-dimensional space. The different expressions of the moving track are interchangeable on the basis of mathematics and geometry, so the communications of modeling technologies between different CAD softwares are viable. The extensible markup language, XML, is a ideal network language, which is fit for the expression and organization of structured data. This paper studies the project "the Web-based management and interchange of three-dimensional CAD data" and gives the resolution. To implement the interchange of the three-dimensional CAD data, it is necessary to summarize the three-dimensional models and modeling technologies, to grasp the consistency of mathematic and geometry. On such basis, we can establish the rules of expressing, organizing and manipulating the related information, and then establish a set of standards to resolve the problem of interchange between different CAD platforms. To implement this goal on the Web, we must select an interchanging mode that is fit for the network application, so we adopt XML to do it. In the paper, the author establishes logic model, explains the related theory and gives an example that proves the theory is viable and right.