56 PART | II ITS users
(Kuutti, 1996) and have an internal and external component with the subject
and object existing as part of a dynamic and reciprocal relationship.
The context model of Kaenampornpan & O’Neil (2004) for activities, as
depicted in Fig. 4.3, captures one more vital context aspect, the time, which
is missing from the basic activity structure of Fig. 4.1. This model comprises
in tandem the past, current, and future aspect of the action context in order to
predict a user’s action from the past and current context.
Activities are not performed in isolation; they influence each other and
are influenced by external activities, objects, and subjects in their context.
According to Kuutti (1996), the interaction between activities or their elements
may cause imbalances, which are referred as contradictions. Contradictions are
FIGURE 4.3 The evolution of activity theory with time. (Adapted from Kaenampornpan and
O’Neil, 2000)
FIGURE 4.2 The hierarchy of activities and the respective context.