It can include personal information such as users' names and ages, their interests, their skills and knowledge, their goals and plans, their preferences and their dislikes or data about their behavior and their interactions with the system.
It depends on the users' readiness to give information and it is unlikely that they are going to edit their answers once the registration process is finished.
Adaptive changes in a system that learns users' preferences and needs only by interpreting their behavior might appear a bit opaque to the users, because they cannot fully understand and reconstruct why the system behaves the way it does.
[5] Moreover, the system is forced to collect a certain amount of data before it is able to predict the users' needs with the required accuracy.
Through collecting data by directly asking its users it gathers a first stock of information which can be used for adaptive changes.
In this case a set of IF... THEN... rules is established that covers the knowledge base of the system.
[2] The IF-conditions can check for specific user-information and if they match the THEN-branch is performed which is responsible for the adaptive changes.
A certain number of representation formats and standards are available for representing the users in computer systems,[8] such as: