where is a value in . Some experiments presented in [13] have shown that is a good value for this threshold.

For the representation schema, we consider that the important terms are those whose frequencies are closer to the TP. Therefore, a term with frequency very ``close'' to TP will get a high weight, and those ``far'' to TP will get a weight close to zero. For each term , its weight, given by Equation (1), is modified according to the distance between its frequency and the transition point, obtaining a new value for its ``term frequency'' (see Equation (7)).

David Pinto 2007-05-08