Hi

> The problem I am having is how to grant privileges to users to securely

allow them to see only the records in selected groups and their children (in
much the same way as a secure file system works).

You can iterate over your parent_item fields inside a stored procedure and
that stored procedure can check for permissions.
It might be better not to include this into the database, but keep it in
your application layer.

From what I am doing, I think database facilities end when it comes to group
permissions, where groups can include other groups...

Remember, that standart sql security only defines special rights to complete
tables.

Regards,
Steffen