http://www.vizrt.com/types/relation/top

This link relation identifies a link to the top (or root) node of a hierarchy. You can use links of this type to navigate from a tag to its owning tag structure, for example.

The following example shows a link of this type:

<entry>
  ...
  <link 
      href="http://host-ip-address/webservice/escenic/classification/tag:folksonomy.escenic.com,2002" 
      rel="http://www.vizrt.com/types/relation/top"
      title="Tags"/>
  ...
</entry>