In this tutorial, you define object classes, assign drawing objects to different classes, and then use the object classes to create, edit, and export drawing objects. To be part of the object class, drawing objects must meet certain rules when they are classified. If you create a drawing object in an object class, it inherits the layer and attribute characteristics of that object class. Object classes help to ensure that drawing objects are standardized.
For example, you can define an object class called Roads and specify its rules:
Then, only line objects that represent 1- to 6-lane roads can be added to the Roads class.
Object classification is helpful when you create metadata. Although the AutoCAD Map 3D toolset Metadata feature generates basic metadata for DWG files, it is optimized for use with maps that use object classes.
Object classification is useful when you are preparing drawing files for export to a spatial data (FDO) format, such as SDF or Oracle. You can export objects based on object classes. Then, each set of exported objects has only the properties assigned to it by its object class.