To formalise this idea into a generative model, we assume that the Giver act g depends only on the Follower act f .
for example, in a flight booking domain, if a user's goal is to fly to London from New York on the 3 rd of November, then the goal takes the form: {origin="New York", dest="London", depart date="03-11-13"}, and expressing the destination takes the form: Provide dest="London".