Adapting to what?--User features

What aspects of the user working with the system can be taken into account when providing adaptation? To which features, that can be different for different users (and may be different for the same user at different time), can the system adapt?

Knowledge--the most important user feature for AH systems

User's knowledge is a variable for a particular user. An adaptive hypermedia system has to recognize the changes in the user's knowledge state and update the user model accordingly.

overlay model -- a set of pairs "concept - value"
stereotype user model -- novice : beginner : intermediate : expert

Goals--a feature related with the context of a user's work

work (in application systems)
search (in information retrieval systems)
problem solving or learning(in educational systems)

Background and Experience

User's background --information related to user's previous experience outside the subject of the hypermedia system
User's experience -- how familiar is the user with the structure of the hyperspace and how easy can the user navigate in it--modeled by a stereotype user model

Preferences

Preferences are used most heavily in IR hypermedia. The user has to inform the system directly or indirectly (by a simple feedback) about such preferences or the system infers user's preferences from user's hostory.