However, despite the implementation of a human-centred design process, some types of modern applications require instant adaptation due to their exposure to increasing situational dynamics.
The operational environment will change, the tasks will be distinct, the end-users will be heterogeneous, and their competences and expectations will evolve.
For this reason, developers implement techniques of adaptation into the system in order to react to changing conditions as fast as possible.
Physiological characteristics like disabilities are of major concern for application designers if they want to have their system accepted by a large community.
Other sources are the user's interests and disinterests, psychological personality characteristics like emotions, self-confidence, motivation, or beliefs, which are difficult to assess automatically.
Moreover, they are frequently required to cooperate spontaneously and opportunistically with previously unknown software services in order to accomplish tasks on behalf of users.