d) Optimized adoption of user profiles: The simple adoption method described above adds all documents (and their affiliation to a class) to the user profile, which have been misclassified by the system. On the long run this leads to two problems: Firstly, the user profile extends without any limit. This reduces the classification performance. Secondly, the system is not able to “forget” anything adopted. This makes an adoption of changes of user’s information demand
impossible. Therefore, it is necessary to develop some kind of reorganisation and garbage collection methods. Qualified data is advantageous for the development of an optimized adoption method. This point belongs to future work and will not be discussed in this paper in more detail.