Appendix B -- Advanced DXF Issues
Persistent Inter-Object Reference Handles
A set of group code ranges permit objects to directly specify references to other objects within the same drawing/DXF file. Four ranges are provided for the four types of reference handles that you can specify:
These handle types are manifested as entity names in AutoLISP, as ads_name values in ObjectARX and as like-named classes derived from ObjectARX. These values are always maintained in insert, xref, and wblock operations such that references between objects in a set being copied are updated to point to the copied objects, while references to other objects remain unchanged.
Also, a group code range for "arbitrary" handles is defined to allow convenient storage of handle values that are not converted to entity names and then translated in insert, xref, or wblock.
NOTE If you use 1005 xdata group codes to store handles, they are treated as soft-pointer handles, which means that when groups of objects are copied or inserted into another drawing, references between the involved objects are translated. Although 1005 xdata items are always returned as handles in AutoLISP® and ObjectARX, all of the reference handle group code ranges are represented as "entity names" in AutoLISP and as ads_name structures in ObjectARX.