Context : The Degtyaryov machine gun (Russian: Пулемёт Дегтярёвa Пехотный Pulemyot Degtyaryova Pekhotny ``Degtyaryov's infantry machine gun'') or DP is a light machine gun firing the 7.62×54mmR cartridge that was used primarily by the Soviet Union starting in 1928. 
Subject : Degtyaryov machine gun 
Relation : service entry
What year was Degtyaryov machine gun commissioned?