INTERACTION: THE TERMS OF INTERACTION, DONALD NORMANâ€™S MODEL

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Human Computer Interaction (CS408)

Lecture 14

Lecture 14. Interaction

Learning Goals

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.

The terms of Interaction

14.1

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

Goals

utensil.

Task

Intention to act

Evaluation of the

Task are the operation to manipulate

Interpretations

the concepts of a domain. A goal is

the desired output from a performed

sequence of

Interpreting the

task. For example, one task within

actions

perception

the graphic design domain is the

construction of a specific geometric

shape with particular attributes on

execution of

Perceiving the state

the drawing surface.

The action sequence

of the world

Goal

A related goal would be to produce a

solid red triangle centered on the

canvas. So, goal is ultimate result,

THE WORLD

which you want to achieve after

performing some specific tasks.

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Donald Norman's Model

14.2

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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Human Computer Interaction (CS408)

The interaction framework

14.3

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

presentation

output observation

Input and the Output. Each

component has its own

language. The system and

user are each described by

means of a language that core

task

can

express

concepts

articulation

relevant in the domain of

performance

the

application.

The

input

system's

language

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.

Frameworks and HCI

14.4

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Human Computer Interaction (CS408)

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

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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Human Computer Interaction (CS408)

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,

system

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

plan

interface

immediate

feedback

instrument

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.

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Human Computer Interaction (CS408)

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.

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Human Computer Interaction (CS408)

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.

Interaction styles

14.5

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.

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

recognition rather than

recall. However, menu

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Human Computer Interaction (CS408)

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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Human Computer Interaction (CS408)

the value of other cells. Now a days MS Excel is used widely. In past VISICALC and

Lotus 123 had been used.

VISICALC

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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