 We may illustrate the idea using discrete time. Assuming that every chronicle in TIME is isomorphic with the set of integers, there will for each chronicle be a function, \(back\), from TIME to TIME such that \(back(t)\) is the moment on the chronicle that is just before the moment \(t\). Furthermore, there is a function \(\next_s\) such that \(\next_s(t)\) is the moment following immediately after \(t\) on \(\TRL_s(t)\).