The user, {HEAD ~ vendor}, manufacturer and other supplier may maintain {TAIL ~ databases} housed on the central computers 
maintain
The user , { HEAD ~ vendor } , manufacturer and other supplier may maintain { TAIL ~ databases } housed on the central computers
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH