Need some feedback. What do you think about storing my data like

Hi,
I need to store a hierarchy in my database (a tree)
I have 3 types of data: Cases, Groups and Users. I can have any
combination of them.
Check the following link ('Groups', 'Cases', 'Users' and 'Tree' will be
tables in my database):
http://www.lemforever.com/temp/tree.jpg
What do you guys think? Do you think is a good solution? I still want to
have a relational database
and I don't want to violate any integrity rules.
Thanks a lot.I just realized that I could have used my previous post for asking that.
Sorry about that.
If you have any feedback please use either one.
Thanks