The base element is "root"; under "root" are "realms" and "policy".
Under "realms" is "ABCrealm". Under "ABCrealm" are "users" and "roles".
Under "users" is "john.singh", which contains "roles" and "permissions". "Roles" contains "manager". "Permissions" contains "java.io.file.permission".
The "roles" link under "ABCrealm" contains "role". "role" contains "users", "roles", and "permissions". "users" contains "user". "roles" contains "role". "permissions" contains "permission."
Under "policy" are "principal-classes" and "permission-classes". Under "principal-classes" is "principal"; under "permission-classes" is "permission".