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As the aim of this lecture is to introduce you the study of
Human Computer
Interaction, so that after studying this you will be able to:
. Define interaction
. Discuss interaction
styles keeping in view different aspects of HCI
In the previous lectures we have studied the detailed
introduction of human side and
computer side. These are two participant of our course Human
Computer Interaction.
As the name of the course reveals that both of these complex
entities are not in
isolation rather they come in contact with each other. Human
communicate with
computers.
There are a number of ways in which human can communicate with
the system. If we
look at the beginning, batch input system was used, in which the
user provides all the
information to the computer in form of batch. Now a day it is
the age of virtual reality
and ubiquitous computing. Here user constantly interacts with
computers in his
surroundings. Today there is richer interaction.
14.1 The terms of Interaction
Domain
A domain defines an area of expertise and knowledge in some
real-world activity.
Some examples of domains are graphic design, authoring and
process control in a
factory. A domain consists of concepts that highlight its
important aspects. In a
graphic design domain, some of the important concepts are
geometric shapes, a
drawing surface and a drawing
utensil.
Task
Task are the operation to manipulate
the concepts of a domain. A goal is
the desired output from a performed
task. For example, one task within
the graphic design domain is the
construction of a specific geometric
shape with particular attributes on
the drawing surface.
Goal
A related goal would be to produce a
solid red triangle centered on the
canvas. So, goal is ultimate result,
which you want to achieve after
performing some specific tasks.
14.2 Donald Norman’s Model
We have already studied Donald Norman’s Model of interaction. In
which user
chooses a goal, formulate a plan of action, which is then
executed at the computer
interface. When the plan, or part of the plan has been executed,
the user observes the
computer interface to evaluate the result of the execution plan,
and to determine
further actions.
The two major parts, execution and evaluation, of interactive
cycle are further
subdivided into seven stages, where each stage is an activity of
the user. Seven stages
of action are shown in figure. To understand these we see an
example, which was also
used by Norman.
Imagine you are sitting reading as evening falls. You decide you
need more light; that
is you establish the goal to get lighter. Form there you form an
intention to switch on
the desk lamp, and you specify the actions required to reach
over and press the lamp
switch. If some one else is closer, the intention may be
different-you may ask them to
switch on the light for you. Your goal is the same but the
intention and actions are
different. When you have executed the action you perceive the
result, either the light
is on or it isn’t and you interpret this, based on your
knowledge of the world. For
example, if the light does not come on you may interpret this as
indicating he bulb has
blown or the lamp is not plugged into the mains, you will
formulate the new state
according to the original goals – is there is now enough light?
It so, the cycle is
completed. It not, you may formulate a new intention to switch
on the main ceiling
light as well.
Gulf of execution and evaluation
Norman also describes the two gulfs, which represent the
problems that are caused by
some interfaces to their users.
Gulf of execution
Gulf of execution is the difference between the user’s
formulation of the actions to
reach the goal and the actions allowed by the system. If the
action allowed by the
system correspond to those intended by the user, the interaction
will effective. The
interface should therefore aim to reduce this gulf of execution.
Gulf of evaluation
The gulf of evaluation is the distance between the physical
presentation of the system
state and the expectation of the user. If the user can readily
evaluate the presentation
in terms of his goal, the gulf of evaluation is small. The more
effort that is required on
the part of the user to interpret the presentation, the less
effective the interaction.
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14.3 The interaction
framework
The interaction framework breaks the system into four main
components as shown in
figure. The nodes represent
the four major components
in an interactive system –
the System, the User, the
Input and the Output. Each
component has its own
language. The system and
user are each described by
means of a language that
can express concepts
relevant in the domain of
the application. The
system’s language is
referred as the core
language and the user’s
language is referred as the task language. The core language
describes computational attributes of the domain relevant to the system state, whereas
the task language
describes psychological attributes of the domain relevant to the
user state. There are
also languages for both the input and output components. Input
and output together
form the interface.
As the interface sits between the user and the system, there are
four steps in the
interactive cycle, each corresponding to a translation from one
component to another,
as shown by the labeled arcs in figure. The user begins the
interactive cycle with the
formulation of a goal and a task o achieves that goal. The only
way the user can
manipulate the machine is through the input, and so the task
must be articulated
within the input language, the input language is translated into
the core language as
operations to be performed by the system. The system then
transforms itself as
described by the operations; the execution phase of the cycle is
complete and the
evaluation phase now begins. The system is in a new state, which
must now be
communicated to the user. The current values of system
attributes are rendered as
concepts or features of the output. It is then up to the user to
observe the output and
assess the results of the interaction relative to the original
goal, ending the evaluation
phase and, hence, the interactive cycle. There are four main
translations involved in
the interaction: articulation, performance, presentation and
observation. The user’s
formulation of the desired task to achieve some goal needs to be
articulated in the
input language. The tasks are responses of the user and they
need to be translated to
stimuli for the input. As pointed out above, this articulation
is judged in terms of the
coverage from tasks to input and the relative ease with which
the translation can be
accomplished. The task is phrased in terms of certain
psychological attributes that
highlight the important features of the domain for the user. If
these psychological
attributes map clearly onto the input language, then
articulation of the task will be
made much simpler.
The ACM SIGCHI Curriculum Development Group presents a framework
and uses it
to place different
areas that relate to
HCI
As you can see in
the figure, the
field of
ergonomics
addresses issues
on the user side of
the interface,
covering input and
output, as well as
the user’s
immediate
context. Dialog
design and
interface styles
can be placed
particularly along the input branch of the framework, addressing
both articulation and
performance. However, dialog is most usually associated with the
computer and so is
biased to that side of the framework. Presentation and screen
design relates to the
output branch of the framework. The entire framework can be
placed within a social
and organizational context that also affects the interaction.
Each of these areas has
important implications for the design of interactive systems and
the performance of
the user.
Let us first take a brief look.
Ergonomics
Ergonomics (or human factors) is traditionally the study of the
physical characteristic
of the interaction: how the controls are designed, the physical
environment in which
the interaction takes place, and the layout and physical
qualities of the screen. A
primary focus is on user performance and how the interface
enhances or detracts from
this. In seeking to evaluate these aspects of the interaction,
ergonomics will certainly
also touch upon human psychology and system constraints. It is a
large and
established field, which is closely related to but distinct from
HCI.
Physical aspects of Interface are as follow:
. Arrangement of
controls and displays
. The physical
environment
. Health issues
. Use of colors
Arrangement of controls and displays
We already have discussed in previous lectures the perceptual
and cognitive issues
that affect the way we present information on a screen and
provide control
mechanisms to the user. In addition to these cognitive aspects
of design, physical
aspects are also important. The user should group sets of
controls and parts of the
display logically to allow rapid access. This may not seem so
important when we are
considering a single user of a spreadsheet on a PC, but it
becomes vital we turn to
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safety-critical applications such as plant control, aviation and
air traffic control. In
each of these contexts, users are under pressure and are faced
with a huge range of
displays and controls. Here it is crucial that the physical
layout of these be
appropriate. Indeed, returning to the less critical PC
application, inappropriate
placement of controls and displays can lead to inefficiency and
frustration.
Industrial Interface
The interfaces to office systems have changed dramatically since
the 1980s. However,
some care is needed in transferring the idioms of office-based
systems into the
industrial domain. Office information is primarily textual and
slow varying, whereas
an industrial interfaces may require the rapid assimilation of
multiple numeric
displays; each of which is varying in response to the
environment. Furthermore, the
environment conditions may rule out certain interaction styles.
Consequently, industrial interfaces raise some additional design
issues rarely
encountered in the office.
Glass interfaces vs. dials and knobs
The traditional machine interface consists of dials and knobs
directly wired or piped
to the equipment. Increasingly, some or all of the controls are
replaced with a glass
interface, a computer screen through which the equipment is
monitored and
controlled. Many of the issues are similar for the two kinds of
interface, but glass
interfaces do have some special advantages and problems. For a
complex system, a
glass interface can be both cheaper and more flexible, and it is
easy to show the same
information in multiple forms.
Indirect manipulation
The phrase ‘direct manipulation,
dominates office system design as
shown in figure (a). there are
arguments about its meaning and
appropriateness even there, but it is certainly dependent on the
user being in primary
control of the changes in the interface. The autonomous nature
of industrial processes
makes this an inappropriate model. In a direct manipulation
system, the user interacts
with an artificial would inside the computer.
In contrast, an industrial interface is merely an intermediary
between the operator and
the real world. One implication of this indirectness is that the
interface must provide
feedback at two levels as shown in figure (b). at one level, the
user must receive
immediate feedback, generated by the interface, that keystrokes
and other actions
have been received. In addition, the user’s action will have
some effect on the
equipment controlled by the interface and adequate monitoring
must be provided for
this.
The indirectness also causes problems with simple monitoring
tasks. Delays due to
periodic sampling, slow communication and digital processing
often mean that the
data displayed are somewhat out of date. If the operator is not
aware of these delays,
diagnoses of system state may be wrong. These problems are
compounded if the
interface produces summary information displays. If the data
comprising such a
display are of different timeliness the result may be
misleading.
The physical environment of the interaction
As well as addressing physical issues in the layout and
arrangement of the machine
interface, ergonomics is concerned with the design of the work
environment itself.
Where will the system be used? By whom will it be used? Will
users be sitting,
standing or moving about? Again, this will depend largely on the
domain and will be
more critical in specific control and operational setting s than
in general computer use.
However, the physical environment in which the system is used
may influence how
will it is accepted and even the health and safety f its users.
It should therefore be
considered in all design.
Health issues
Perhaps we do not immediately think of computer use as a
hazardous activity but we
should bear in mind possible consequences of our designs on the
health and safety of
users. Leaving aside the obvious safety risks of poorly designed
safety-critical
systems. There are a number of factors in that may affect the
use of more general
computers. Again these are factors in the physical environment
that directly affect the
quality of the interaction and the user’s performance:
Physical position
As we discussed earlier users should be able to reach all
controls comfortably and see
all displays. Users should not be expected to stand for long
periods and, if sitting,
should be provided with back support.
Temperature
Although most users can adapt to slight changes in temperature
without adverse
effect, extremes of hot or cold will affect performance and, in
excessive cases, health.
Lighting
The lighting level will again depend on the work environment.
However, adequate
lighting should be provided to allow users to see the computer
screen without
discomfort or eyestrain. The light source should also be
positioned to avoid glare
affecting the display.
Noise
Excessive noise can be harmful to health, causing the user pain,
and in acute cases,
loss of hearing. Noise level should be maintained at a
comfortable level in the work
environment.
Time
The time users spend using the system should also be controlled.
The use of color
Ergonomics has a close relationship to human psychology in that
it is also concerned
with the perceptual limitations of humans. For example, the use
of color in displays is
an ergonomics issue. The human visual system has some
limitations with regard to
color, including the number of colors that are distinguishable
and the relatively low
blue acuity. Color used in display should be as distinct as
possible and the distinction
should not be affected by changes in contrast. The colors used
should also correspond
to common conventions and user expectation. However, we should
remember that
color conventions are culturally determined.
14.5 Interaction styles
Interaction is communication between computer and human (user).
For a successful
enjoyable communication interface style has its own importance.
There are a number of common interface styles including
. Command line
interface
. Menus
. Natural language
Question/answer and query dialog
. Form fills and
spreadsheets
. WIMP
. Point and click
. Three-dimensional
interfaces.
Command line interface
Command line interface was the first interactive dialog style to
be commonly used
and, in spite of the availability of menu-driven interface, it
is still widely used. It
provides a means of expressing instructions to the computer
directly, using some
function keys, single characters, abbreviations or whole-word
commands.
Command line interface are powerful in that they offer direct
access to system
functionality, and can be combined to apply a number of tools to
the same data. They
are also flexible: the command often has a number of options or
parameters that will
vary its behavior in some way, and it can be applied to many
objects at once, making
it useful for repetitive
tasks.
Menu
In the menu-driven
interface, the set of
options available to the
user is displayed on the
screen and selected using
the mouse, or numeric or
alphabetic keys. Since the
options are visible they
are less demanding of the
user, relying on
recognition rather than
recall. However, menu options still need to be meaningful and logically grouped to aid
recognition. Often
menus are hierarchically ordered and the option required is not
available at the top
layer of the hierarchy. The grouping and naming of menu options
then provides the
only cue for the user to find the required option. Such systems
either can be purely
text based, with the menu options being presented as numbered
choices, or may have
a graphical component in which the menu appears within a
rectangular box and
choices are made, perhaps by typing the initial letter of the
desired selection, or by
entering the associated number, or by moving around the menu
with the arrow keys.
This is restricted form of a full WIMP system.
Natural Language
Perhaps the most attractive means of communicating with
computers, at least at first
glance, is by natural language. Users unable to remember a
command or lost in a
hierarchy of menus, may long for the computer that is able to
understand instructions
expressed in everyday words. Unfortunately, however, the
ambiguity of natural
language makes it very difficult for a machine to understand.
Question/answer and query dialog
Question and answer dialog is a simple mechanism for providing
input to an
application in
a specific domain. The user is asked a series of questions and
so is led through the
interaction step by step. An example would be the wizards as
shown in figure.
These interfaces are easy to learn and use, but are limited in
functionality and power.
As such, they are appropriate for restricted domains and for
novice or casual users.
Query languages, on the other hand, are used to construct
queries to retrieve
information from a database. They use natural-language-style
phrases, but in fact
require specific syntax, as well as knowledge of database
structure. Queries usually
require the user to specify an attribute or attributes for which
to search the database,
as well as the attributes of interest to be displayed. This is
straightforward where there
is a single attribute, but becomes complex when multiple
attributes are involved,
particularly of the user is interested in attribute A or
attribute B, or attribute A and not
attribute B, or where values of attributes are to be compared.
Most query language do
not provide direct confirmation of what was requested, so that
the only validation the
user has is the result of the search. The effective use of query
languages therefore
requires some experience.
Form-fills and spreadsheets
Form-filling interfaces are used primarily for data entry but
can be useful in data
retrieval applications. The user is presented with a display
resembling a paper form,
with slots to fill in as shown in figure. Most form-filling
interfaces allow easy
movement around the form and allow some fields to be left blank.
They also require
correction facilities, as users may change their minds or make a
mistake about the
value that belongs in each field.
Spreadsheets are sophisticated variation of form filling. The
spreadsheet comprises a
grid of cells, each of which can contain a value or a formula.
The formula can involve
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the value of other cells. Now a days MS Excel is used widely. In
past VISICALC and
Lotus 123 had been used.
The WIMP Interfaces
Currently many common environments for interactive computing are
examples of the
WIMP interface style, often simply called windowing systems.
WIMP stands for
windows, icons, menus, and pointers, and is default interface
style for the majority of
interactive computer systems in use today, especially in the PC
and desktop
workstation arena.
Point and Click interface
In most multimedia systems and in web browsers, virtually all
actions take only a
single click of the mouse button. You may point at a city on a
map and when you
click a window opens, showing you tourist information about the
city. You may point
at a word in some text and when you click you see a definition
of the word. You may
point at a recognizable iconic button and when you click some
action is performed.
Three-dimensional interfaces
There is an increasing use of three-dimensional effects in user
interfaces. The most
obvious example is virtual reality, but VR is only part of a
range of 3D techniques
available to the interface designer.
The simplest technique is where ordinary WIMP elements, buttons,
scroll bars, etc,,
are given a 3D appearance using shading, giving the appearance
of being sculpted out
of stone. |
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