add new user type in jos_core_acl_aro_groups

[vaishnavi]

hi,
I am using virtuemart in Joomla.
I have to create a new user type 'artist'.
For that i have to add 'artist' in jos_core_acl_aro_groups table.
In the table ,the lft and rft of the nodes are added.
Can any one tell me which algorithm has been used to assign left and right child for a node?
I think the algorithm used is DLR(Data-Left-Right) tree traversal algorithm.
When i traversed the tree using DLR , half of the tree traversal produced correct left/right node numbers.
According to my traversal 'public backend' comes out as 13,but in the table it is 21.
I am not getting this.
Without knowing the values i won't be able to execute the insert query for 'artist'
Can anyone explain me this?

Reply.

Thank you.