First, obviously, [t] precedes [t'] if all instants in [t] precede all instants in [t']. But [t] may also precede [t'] if they overlap, as we saw in chapter 5.2 with the half-open interval [to,to+ I) including to but not to+ 1, which precedes the half-open interval (to,to+ I] that includes to+ 1 but not to' Here [t] precedes [t'] because some instant in [t] precedes all instants in [t'] but not vice versa; and similarly in other cases.