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Unformatted text preview: een the user’s existing knowledge and the knowledge needed for an
effective interaction. For instance, when the word-processor were initially introduced,
the similarity between the word-processor and a typewriter was intended to make the
new technology more immediately accessible to those who had some experience with
the typewriter (Dix et al., 1993).
Generalizability is refers to the support for the user to expand knowledge of specific
interaction within and across applications to other similar situation. Generally, users try
to widen their knowledge of specific interaction behavior to similar situations however
previously remain un-encountered. The generalizability of an interactive system hold-up
this activity that leads to a more complete predictive model of the system for the user.
Generalization can be applied in such situations in which the user wishes to apply
knowledge which help to achieve a particular goal or the goal is somehow similar (Dix
et al., 1993).
Consistency has been a widely discussed field of user interface design. Consistency
refers to the likeness in behavior arising from similar situations. Generally, user relies
on a consistent interface; however, the difficulty of dealing with consistency is that it
can be of many kinds. Consistency is not just a single property of an interactive system
that is either satisfied or dissatisfied. Consistency can also be demonstrated in terms of
the form of input expression or output responses with respect to the meaning of actions
in some conceptual model of the system (Dix et al., 1993). 25 2.5.2 Flexibility Flexibility relates to the multiplicity of ways the end-user and the system exchange
information. The principles, which contribute in the flexibility, are explained as
Dialogue initiative relates to allow the user freedom from artificial constraints on the
input dialogue forced by the system. In order to make a relation between user and
system as a dialogue between partners, it is important to consider that which partner
make initiative in the dialogue. The system can initiate all dialogues, in that case the
user simply request for information; this type of dialogue is called system pre-emptive.
For instance, a sample dialogue box prevents the user from interacting with the system
that does not direct the input to the dialogue box. On the other hand, the user may be
entirely free to initiate any action towards the system, in such case the dialogue is called
user pre-emptive. The system may control the dialogue to the extent that it prevents the
user to commence any other desired communication regarding the current task or some
other task that the user would like to execute. From the user’s point of view, a systemdriven interaction hinders flexibility whereas a user-driven interaction favors it (Dix et
Multi-threading refers to the ability of the system to support user interaction relating to
do multiple tasks simultaneously. A thread of a dialogue is a rational subset of that
dialogue. In the user-system dialogue, we can consider a thread to be that part of the
dialogue that relates to a given user task. Multi-threading of the user-system dialogue
allows for interaction to support more than one task at a time. Concurrent multithreading allows simultaneous communication of information relevant to separate tasks.
Interleaved multi-threading allow a temporal overlap between separate tasks but
stipulates that at any given instant, the dialogue is limited to a single task (Dix et al.,
Task migratability is the ability to pass control to carry out a given task so that it
becomes either internalized by user or system or shared between them is referred as task
migratability. It should be feasible for the user or system to pass the control of a task
over to the other and promote the task from an entirely internalized one to a shared and 26 cooperative project. As a result, a task that is internal to one can become internal to the
other or shared between the two associates. The spell check in word-processing is a
good example of the need for task migratability. It is equipped with an embedded
dictionary and user can perfectly able to check spelling by reading throughout the paper
and correct mistakes which left or missed during typing (Dix et al., 1993).
Substitutivity refers to allowing equivalent values of input and output to be randomly
substituted for each other. Substitutivity demands that equivalent values should be
substituted for each other, for instance, in word processing the input of letter size or
margin can be set either by inches or by centimeters. This input value can be entered in
form of calculation which generates the right input value of the text. This input
substitutivity adds toward flexibility by allowing the user to choose whichever form
best suits the needs of the situation. Therefore, by avoiding unnecessary calculations in...
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