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User Modeling for Personalized Web-Based Systems 227
Explicit User Modeling
Explicit user modeling consists of letting a user to fill-in a prepared set of forms and is the
most basic approach used by the majority of adaptive systems. The system asks the user
for all information needed for successful adaptation (or at least information to initialize the
user model). This approach is used on almost every system to acquire at least some basic
information about a user (see Figure 8-5).
Figure 8-5. Part of a registration form of an adaptive educational system ELM-ART.
The advantage of this approach is the possibility to acquire practically any kind of information
about user – even such information which can not be acquired automatically.
It is easy to believe that a substantial advantage is a high credibility of acquired information.
It is natural, as the source of information (the user) is, in the same time, the subject the
information is related to. However, it can easily happen that a user does not know the exact
answer to given questions, she does not know a value of some required characteristic.
Another complication of credibility of information supplied by users comes from subjective
point of view when they should evaluate their skills. User can easily overestimate
or underestimate the real value of a characteristic (e.g., user might think she has a good
knowledge on particular programming language even if it is not true).
Yet another severe drawback of classical form approach is the complexity of graphical
user interface. For example to provide preferences on movies, the Internet Movie Database
provides a Power Search mode 5 which allows users to combine several criterion to get
more precise movie retrievals. For example, users can require certain cast or keywords in
the plot summary and filter by genre, year, and other options. The search user interface
5 IMDB Power search, http://us.imdb.com/list/