ABBA NETWORK

Although research on games has been mathematically formalized only relative
recently, related insights can be traced back to philosophers from ancient times.
As an example, at one point Socrates sketches the setting of a soldier waiting
with his comrades to repulse an enemy attack. He reasons that if the battle will
be won, the e®ort of the soldier is not needed and therefore he would better not
participate, avoiding risk of injury. On the other hand it the battle will be lost,
the soldiers chance of getting hurt are even higher and therefore, he should not
participate in the battle in this case either. This kind of reasoning is very much
related to ideas in current game theory.

In the ¯rst half of the twentieth century a lot of research was performed on
games. Important contributions were made by Zermelo, von Neumann, Morgenstern
and Nash and others, leading to a formalization that could be called
the `classical game theory’.

With the advent of computers, again lots of games have been studied. Until
the late 90’s, most of the e®ort focused on fully observable games. An example
of a fully observable game on which computer science research focused is
backgammon. In 1992 TD-Gammon was introduced in [57]. The program was
able to compete with the world-class player winning some games losing some
others.

The most prominent, however, was the research performed on chess: the literature
on chess is extensive including dedicated journals. This research resulted
many advances in computer science, especially search techniques. In 1997 for
the ¯rst time the world-champion at that time, Garry Kasparov, was defeated
by a computer, `Deep Blue’.

Since then more and more attention has shifted to partial information games.
Poker was identi¯ed as a next `benchmark’ problem for partial information
games [1, 5] and indeed more and more research has focused on poker in the
last decade.