  Although largely unnoticed by the online algorithms community, T-theory, a
field of discrete mathematics, has contributed to the development of several
online algorithms for the k-server problem. A brief summary of the k-server
problem, and some important application concepts of T-theory, are given.
Additionally, a number of known k-server results are restated using the
established terminology of T-theory. Lastly, a previously unpublished
3-competitiveness proof, using T-theory, for the Harmonic algorithm for two
servers is presented.
