Log Sarkisov Program

The purpose of this paper is two-fold. The first is to give a tutorial introduction to the Sarkisov program, a 3-dimensional generalization of Castelnuovo-N\"other Theorem ``untwisting" birational maps between Mori fiber spaces, which was recently established by Corti after Sarkisov and Reid. The second is an attempt to give a logarithmic generalization of the program, introducing the notion of the Sarkisov relation. We give a simple description of the structure of the program and clarify the mechanism of termination connected to the boundedness conjecture of (log) Q-Fano n-folds by Borisov.