at front, fronter, fronting

Front is the metaphorical region of our system which exists at the interface between us and the world around us. The interior of this conceptualized space can be most readily matched against the region between front and [elsewhere]. Someone who is considered 'in system' is near enough front for their presence to be felt by those at front, and those 'near front' are close enough to pay attention to specific external events but not the entirety of our situation.