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226 Selected Studies on Software and Information Systems
cold-start problem. However, personalization could be crucial if we want to attract the user
and motivate him or her to use the system [61].
In fact, the adaptation is probably of highest benefit exactly to a new user of the system,
which is not at all familiar with the domain nor the graphical user interface of the system and
can not express clearly her requirements. System should pay a special attention to such user
and should try to facilitate her first experience or it could easily happen that the user would
get lost, confused and never returns again. Cold-start problem is generally being solved by:
– initializing the model by pre-defined values;
– acquiring needed information directly from the user or from user’s behavior;
– using the knowledge from user models of users already present in the system;
– bootstrapping the user model from external sources.
8.5.1 Initializing the Model by pre-Defined Values
This is probably the most simple form of user modeling. For example, a great number of
educational systems assume that a new student knows nothing (or that all users have some
standard prior knowledge) about the domain and thus initialize the knowledge on all domain
concepts to one pre-defined value [61]).
This category encompasses also the stereotype-based approach. According to [34] (as
cited in [61]) a stereotype consists of three main components:
1. a set of trigger conditions;
2. a set of retraction conditions;
3. a set of stereotype inferences.
Trigger and retraction conditions are boolean expressions that activate or deactivate an active
stereotype. Stereotype inferences of the particular stereotype serve as default assumption
for the user, used for adaptation. However, stereotype-based approach is often considered
static, meaning that the stereotype is assigned at the beginning of the user’s work and is
not changing ever after (in fact, the stereotype can be “forgotten” when it is used only for
initialization of an overlay user model).
8.5.2 Acquiring Information from the User and from User’s Behavior
Approaches to acquisition of information from the user can be discriminated into two categories:
– explicit, where user is providing information explicitly, by some special type of interaction
(usually by filling-in a form);
– implicit, where system tracks user activity within the system and use this as a base for
estimating and/or inferring the desired information.