DXF Group Codes
Advanced DXF Issues
A big problem with filing a stream of group data is that a single object may be composed of several filer members, one for each level of inheritance where filing is done, which can be done by different developers. Because each level of inheritance can evolve separately, it is necessary to segregate the data of each class filer member from each other.
All class filer members are expected to precede their class-specific portion of instance data with a "subclass" marker--a 100 group code followed by a string with the actual name of the class. This does not affect the state needed to define the object's state, but it provides a means for the DXF file parsers to direct the group codes to the corresponding application software.
For example, an object which has data from different derived classes would be represented as follows:999