When a MicroStation PowerDraft design file used as a reference has its own attachments, they become nested references. The links between these files can be maintained through many levels (depths) of nesting, so that if you open only one file, you can view the contents of many files. The individual references can be updated, and the changes will be shown in the master (or parent) file. When you attach a parent reference to your model and turn on live nesting, you can also control how many levels of nested references are attached to the model.

In AutoCAD, there are two types of references that can be made to create file associations — attachments and overlays. Both allow the display of all objects in the attached file, as well as those in the nested references. Although AutoCAD allows live nested references, it does not provide control of nesting depth, and thus all data in the nested attachments is implicitly displayed.