Biomedical Engineering Reference
In-Depth Information
achieve the information they are looking for). However, when the relationship between
accessibility and usability is defined in this bi-polar way, accessibility might be estab-
lished as the objective end of the user interaction, while usability could be correlated
to the subjective aspects, as determined by users' inherent individual differences. From
this perspective, a technological product is reduced to a neutral entity that functions
independently from its user in a neutral environment. As a result, a machine could be
perfectly accessible but not usable. Consequently, usability does not pertain at all to
the technological aspects of a machine functioning, but to the cognitive and functional
aspects of the individual differences. (2010, p. 2).
Therefore, as Federici and colleagues (2005) state, when objective and subjective elements
are referred to accessibility and usability in a user-computer interaction, they cannot be
considered as separate entities, but as two different moments both included in the con-
tinuum of empirical observation. Each entity is not considered separately from its observer
during the interpretative/reconstructive process because the entity is known by the sub-
ject only as an observed and perceived object (Figure 15.3).
From this viewpoint, accessibility and usability are not understood as characteristics
regarding two separate interacting entities but rather as one intrasystemic relation in which
both object and subject are just moments in a multiphase process of empirical observation.
This prevents the existence of userless technological products, thereby guaranteeing that
the accessibility of a machine always refers only to the possible entrance and exit of a
signal needed to fulfill the task for which it was designed, and that it is in constant relation
either to its designer or to its user. In this sense, a machine should not be accessible and yet
unusable at the same time.
Objective
oriented
Level accessibility and usability
conformance to the rules
System
Evaluation
Intrasystemic relation
User
Subjective
oriented
Problems and satisfaction of the
interaction (accessibility and usability)
measured by the evaluator
observing the users
FIgUre 15.3
(
See color insert.
) The possible evaluation perspectives during the evaluation of the intrasystemic dialogue
between user and system: the objective-oriented and the subjective-oriented perspectives. The interaction eval-
uation has to take into account not only the properties of a single dimension (the accessibility or the usability),
but also the relations that bind the objective part of the interaction to the subjective one (and vice versa). In this
context, accessibility and usability are considered as necessary steps for the evaluation of the intrasystemic
relation between interface and user.
