Also, I tend to think along the lines of...
Type X
End Type
Type Y Extends X
End Type
Type Z Extends Y
End Type
X and Y are both base types of Z. However, only Y is Z's super type - ie: 'immediate' base type.
Type X
End Type
Type Y Extends X
End Type
Type Z Extends Y
End Type
X and Y are both base types of Z. However, only Y is Z's super type - ie: 'immediate' base type.