File types have a direct bearing on the format of the file and he manner in which it should be named. File types include models, details, sheets,, schedules, text, databases, symbols,borders, and title blocks. The file- and layer-naming system discussed here follows the AIA CAD Guidelines, as astablished by the U.S. National CAD Standard.
A building model file is an electronic representation of the building. Models may be two- or three-dimensional and are created at a 1:1 scale. All geometry in a model file contains a three-dimensional coordinate (x,y,z). In two-dimensional drawings, the z coordinate is O.
The electronic sheet file contains one or more views of one or more model files, as well as text, symbols, and, often, a border or title block. The title block generally contains graphic and text information common to all other sheets in a project or section.