A tool to obtain a classifier system from labelled databases is presented. The result is a hierarchical set of rules to divide the space in n-orthohedrons. This hierarchy means that obtained rules must be applied in specific order, that is, an example will be classify by i-rule only if it isn't matched the conditions of the i-1 preceding rules. It is used a genetic algorithm with real codification as searching method. Logically, computation time will be greater than other systems like C4.5, but it will provide flexibility to the user because it is always possible to produce rules set with 0% of error rate and, from here, to relax the error rate for having less rules. Afterwards, a qualitative approach is made to obtain a linguistic rule set. Finally, several results are summarized in section 4.