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