  We propose an online form of the cake cutting problem. This models situations
where players arrive and depart during the process of dividing a resource. We
show that well known fair division procedures like cut-and-choose and the
Dubins-Spanier moving knife procedure can be adapted to apply to such online
problems. We propose some desirable properties that online cake cutting
procedures might possess like online forms of proportionality and
envy-freeness, and identify which properties are in fact possessed by the
different online cake procedures.
