Hierarchies are groups of interrelated data records, each domain can have a set of hierarchy tables and these tables can be used to store specific data for different types of hierarchies. For example, consider a hierarchy that models the relationships between a legal entity and its owning company:
Start Date | Date Time |
End Date | Date Time |
Ownership PC | Numeric |
Status | Status |
Subsidiary | Checkbox |
We could define a table much like a standard data table, however in the table properties we can check the option:

Use for relationship data prevents the table from appearing under the search and add fields and also as a foreign key linkage, but it enables it to be used a a method to collect data when you are adding a relationship between two nodes in a hierarchy:

Restricted Relationships will force the hierarchy to only be built from nodes of the same table, ie Company-Company.