Information is perhaps the most important ingredient for all computational tasks.
It is generally true that the more input information is given, the better algorithmic performance one can expect. The common denominator of such problems is the constraint that one must maka decisions without complete information. This book concerns the problem of computing with incomplete information. In particular, it focuses on a common scenario where the input is given one piece at a time, and upon receiving an input, the algorithm must take an irreversible action without the knowledge of future inputs. That is, once an action is taken, either we cannot undo it at all or the undoing will incur a cost, which adversely affects the overall performance of our algorithms.