The objective of a task oriented SDS is to fulfill the users goal, but as the goal is not observable for the SDS, the SDS needs to gather enough information to correctly fulfill it.
in each turn, the DM can decompose its decision in two steps: first, decide between taking an action in order to gather information about the user goal (information gathering actions) or taking an action to fulfill the user goal or a part of it (information providing actions) and second, select a (primitive) action to execute from the previously selected subset.