Root Node design for a hierarchy/treeview in the user interface

Question

I want to display hierarchical data in the user interface in a treeview control.

The question is should the user has the freedom to define its first root node itself.

I do not care wether a tree has a root node to be a tree.

I just think about the advantage for the user having a pre-defined root node or not in the UI.

Do you see any disadvantage for the usability or that the user could be restricted from

certain posibilities having a pre-defined root node?

In my opinion the root node has this disadvantage:

• its just a stupid placeholder for nothing, just there so the children are there...
• it can usually not be deleted, thus I have to do extra checks...
• I have to think about a creative name for the root node

Do not need:

MySuperRootNode
  11
  12
    21
    22

Totally fine should be:

1
  11
  12
2
  21
  22

Answer 1

I can't answer from a mathematical perspective, but from a UX perspective the root node is not required if it conveys no information about the hierarchy, and especially if it is liable to cause confusion about what the root actually represents.

The primary reason for including a root node is to represent an actual object which is a superclass of all its descendants. For example, in web design, the home page on a website can fill this role (depending on the site's IA). On the other hand, if there is no actual object that the user would want to interact with at this level on the hierarchy, it makes sense to not present an arbitrary object to the user for the sake of completeness.