One solution of this dilemma is the use of an adaptive approach. The idea is to present some evaluated documents to the IF system and to let it generate the user profile on its own. As a side-effect the system can improve the user profile continuously if the user himself gives a feedback on misclassified documents. This approach has already been implemented in NewsSIEVE [Haneke 2001] and PI-Agent [Kuropka 2001] systems. NewsSIEVE adapts the user profile by using evolutionary algorithms while the PI-Agent uses neuronal networks. Both approaches have in common that the initial
information about user profiles (= training set) are transformed into an internal representation (e. g. neuron
weights in case of a neuronal network) which makes the profile representation difficult to understand for users. So the system is not able to explicate its classification rules in a user-friendly way. This leads to the following problems: Firstly, the user has to rely on the classification given by the IF system without knowing how the classification is done in detail. Secondly, in case the user’s information demand shifts from one day to another or the system is unable to adapt his information demand, it is impossible for him to make reasonable corrections on his profile. Consequently, the user has to wait until the system has corrected his profile automatically. Meanwhile, a lot of documents may be misclassified.