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User Modeling for Personalized Web-Based Systems 229
beginning and one for the end of an interval, during which the system presumes that a page
was displayed on user’s screen. The system uses this information to infer user’s knowledge
on a related concept(s). The approach presumes that if the page was displayed, the user read
it and hopefully understood it. This presumption can not be guaranteed to be true all the
time, but the approach is achieving good results anyway, when system is used intensively
enough.
Monitoring access to resources can be used also in other domains, e.g., in scientific
publication domain we would acquire records about displayed publications. However, the
interpretation of these records needs to be more complex than in educational domain. We
can presume, that while searching for suitable publication user will find such papers, which
are not of her interest. In this case, the simple list of displayed publications does not give
a complete information, which could be used in the characteristics discovery process. We
need to know the way how the user navigated to the results and/or user’s feedback to
individual items.
Monitoring User Feedback This approach is an extension of the above mentioned one,
which processes user’s feedback on the proposed content. We can divide user’s feedback
according to the nature of its acquisition, in the same way as the general acquisition of
information from the user, into explicit and implicit feedback.
Explicit Feedback. This type of feedback is acquired when the user explicitly utter her
attitude to the displayed content. This is usually done by rating it on a given (often Likert)
scale [63].
Explicit feedback is considered to be a good source of user preferences, but one need
to design it carefully from the HCI perspective, otherwise the results could be biased. We
can apply the HCI key constructs to questionnaires such as Perceived ease of use, Perceived
usefulness, Disorientation or Flow. These constructs may depend on the presentation (response
format and questionnaire layout) as well as interaction mechanisms that are employed in the
administration of scale items [63].
Especially important are Perceived usefulness which is defined as the degree to which a user
believes that making a rating would give her some benefits and Flow which is a psychological
state in which a person feels cognitively efficient, motivated and happy. When people are
in the state of flow, they become absorbed in their activities and irrelevant thoughts and
perceptions are screened out (as cited in [63]). It is important that questionnaires do not
break this flow but rather become a part of it.
Implicit Feedback. Because explicit feedback acquisition is not reliable (user oversees
the rating widget or is not motivated to rate items) research is oriented also on implicit
feedback which is derived from the usage of the system. It is an estimation how would user
explicitly rate the particular item.
Observable behavior for implicit feedback is stated in [51]. Authors define three main
categories of behavior: examination, retention and reference. The most interesting category,
from the perspective of web-based systems, is examination which encompasses following
behavior: