Example with shows the uses of id, DEF for USE and ROUTE references. X3D uses DEF to name nodes and HTML usually id. We support both in X3DOM with a simple rule.
A) If both id and DEF are set both attributes will have differnt values
B) If only DEF is given id is unset
C) If only id is given DEF and id will be set
Therefore you can use id-names for USE and ROUTE references as shown in this example.