1. A method for determining important attributes for discriminating between different values of a label attribute, the method comprising the steps of: receiving a set of records, each record having a plurality of attributes; permitting a user to choose the label attribute; permitting a user to choose at least one first attribute that is considered important; generating at least one second important attribute, said generated at least one second important attribute together with the said chosen at least one first important attribute discriminate well between the different values of the label attribute; generating non-cumulative purity for each of said chosen at least one first important attribute and each of said generated at least one second important attribute, said non-cumulative purity indicating how well each first and second important attribute individually discriminates between different values of the label attribute; and generating cumulative purity for each of said chosen at least one first important attribute and each of said generated at least one second important attribute, said cumulative purity indicating how well a respective important attribute in combination with other first and second important attributes discriminates between different values of the label attribute.