Title:    A rule based expert system for hitting technique 
          in amateur tennis competition

Authors:  Eugenio Roanes-Lozano
          (Univ. Complutense de Madrid, Madrid, Spain)

          Eduardo A. Casella
          (Club SportOcio Alcantara, Badajoz, Spain)

          Fernando Sanchez
          (Univ. de Extremadura, Badajoz, Spain) 
          
          Antonio Hernando
          (Univ. Politecnica de Madrid, Madrid, Spain)

Extended Abstract:

There are many aspects in tennis teaching that have to be
addressed (tactic, technique, physical training,...) and a coach
is clearly needed for improving the player's level. For instance,
the biomechanical of a stroke is only clear to the expert's eyes.
But most amateur tennis players are not accompanied by a coach
when playing championships, and sometimes a hint like "hit the
ball at a higher point when you serve" can change a match. 

We would like to address here just this aspect of the whole 
process: finding out what's going wrong in a certain match with 
respect to the player's usual technique. We have developed a rule 
based expert system that applies inference to the answers of the 
player to a set of questions regarding both the problem and the 
player's usual technique. 

It requires a certain knowledge of the technique from the player 
(it is focused to amateur competition players, not to beginners). 
Therefore, this is neither a system devoted to learn how to play 
tennis, nor a substitute for a coach. It only tries to correct 
mistakes in a stroke going wrong along one match and returning 
the situation to the usual one. The article is illustrated with 
the part of the system corresponding to the serve.

The expert system is based on Boolean propositional logic and the
inference engine makes use of Groebner bases and is implemented 
in the computer algebra system Maple.

The first and third authors of this paper are mathematicians and 
also veteran tennis players. The first one is a tennis instructor 
ranked nowadays among the 500 top players in Spain. The second 
author is their tennis coach, an "ITF Level 2 Tennis Coach" with 
a long experience in teaching tennis and coaching tennis players 
both in Argentina and Spain. Finally, the fourth author is an 
experienced expert systems developer.