storing the protection level of each of {HEAD ~ the set} of {TAIL ~ data} stored in the leaf nodes; and 
storing the protection level of each of { HEAD ~ the set } of { TAIL ~ data } stored in the leaf nodes ; and
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH