The graphical representation of FRED document data hierarchy is shown in the Object Tree View, the graphical nature of which makes the organization of the data clear.

In the example object tree view below, the subassembly named Houghton corrector is the parent node of elements Lens 1 and Lens 2.  The Geometry node is the parent node of the subassembly Houghton corrector.  The textual representation of the data hierarchy follows from the graphical representation, where parent and child node relationships are denoted with a “.”.  The equivalent text string identifier for Surface 1 of Lens 1 is shown below.

The text string identifier is most commonly used in FRED's scripting language to return the unique node id number of an entity on the object tree.  Typically, the text string identifier of an entity is passed to a function as an argument and the unique node id number is returned for use in the remainder of the script.