The data encoded by each tag includes an identity of the product item, {HEAD ~ an identity} of the interface surface and the position of {TAIL ~ the respective tag} on the interface surface 
The data encoded by each tag includes an identity of the product item , { HEAD ~ an identity } of the interface surface and the position of { TAIL ~ the respective tag } on the interface surface
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH