 There will be a set Moments of instants or intervals of time during the trip. She will start the trip at the location \(\const{Hotel}\) and moment \(\const{Start}\), and end it at the location \(\const{Farm}\) and moment \(\const{Finish}\). Moments will have type \(\tau\), and locations will have type \(\varrho\). A state will have type \(\sigma\) and will specify the location of Sheila, the ostrich, and the cheetah at a given moment. A plan will specify where the entities will be at each moment according to this plan. It will be a function from moments to states, and will have type \((\sigma \tau)\). The exact representation of states need not concern us, but there will be functions from states to locations called \(\const{LocationOfSheila}\), \(\const{LocationOfOstrich}\), and \(\const{LocationOfCheetah}\) which provide the indicated information. Thus, \(\const{LocationOfSheila}_{\varrho \sigma}[p_{\sigma \tau}t_{\tau}]\) will be the location of Sheila according to plan \(p_{\sigma \tau}\) at moment \(t_{\tau}\). The set \(\const{Proposals}_{{o}(\sigma \tau)}\) is the set of plans Sheila is considering.