Data is also the Operations officer, basically from what I have also though is that the Ops officer is in charge of everything sans warp core, which includes the ships hull, superstructure, etc. They also work as a direct liason with engineering so as to not have to rely on verbal communication only. Data and Harry also appeared to be the ship's "machine" shop, developing, analyzing and installing new equipment.
Commander William T. Riker: My great-grandfather once got bit by a rattlesnake. After three days of intense pain... the snake died.