Characteristics of Good Human-Computer Dialogues

Howell Istance

Overview Types of dialogues Message passing in dialogues Initiative in dialogues Characteristics of “Good Dialogues”

Consistency Support Feedback Minimal input Flexibility

Types of Dialogues Message passing model

Dialogue is viewed as an exchange of messages of different types between the human and the computer, rather like a human-human dialogue.

Object-oriented modelDialogue allows the user to manipulate objects represented in the computer, and the computer responds by showing the current state of the objects. interface objects - windows, buttons etc. application objects - paragraph, appointment, customer

order etc.

Message passing in dialogues

SYSTEM

Input

Output

controldata

promptdata

statuserrorhelp

Message passing in dialogues

Input control user directs way in which dialoguewill proceed

data data supplied by user

Output prompt request for user input

data data from application following user request

status acknowledgment that something has happened

error processing cannot continue

help additional information to user

Messages in human-human dialogue

(long period of phone ringing....)

British Rail enquiries.

Can I help you?

Yes, I want to check an arrival time please.

For which train sir?

The 14.05 from Leicester to London.

On which day?

Saturday.

There is no 14.05 on Saturdays.

Oh. When are the trains on Saturday?

There’s the 14.30, the 15.15 and the 16.00.

How about the 14.30?

That gets in at 15.50.

Messages in human-human dialogue

(status)

(prompt)

(input control)

(prompt)

(input data)

(prompt)

(input data)

(error)

(input control)

(help)

(input data)

(output data)

(long period of phone ringing....)

British Rail enquiries.

Can I help you?

Yes, I want to check an arrival time please.

For which train sir?

The 14.05 from Leicester to London.

On which day?

Saturday.

There is no 14.05 on Saturdays.

Oh. When are the trains on Saturday?

There’s the 14.30, the 15.15 and the 16.00.

How about the 14.30?

That gets in at 15.50.

Initiative and dialogue styles

Computer initiates dialogue Question and answer (interview analogy) Menu (menu analogy) Hypertext or embedded icons (can be seen as a type of menu)

Form fill (paper form analogy) User initiates dialogue

Command (parade ground analogy)

Mixed mode dialogues Very common situation Uses several of the above styles

e.g. form-fill dialogues with scrollable menus to provide input

Characteristics of good dialogues

Consistency Appropriate User Support

navigation information instructions error messages provision of help

Adequate feedback from system Minimal user input Flexibility Good visual appearance Close match to tasks of user

Characteristics of good dialogues

Consistency Appropriate User Support

navigation information instructions error messages provision of help

Adequate feedback from system Minimal user input Flexibility Good visual appearance Close match to tasks of user

General

Characteristics of good dialogues

Consistency Appropriate User Support

navigation information instructions error messages provision of help

Adequate feedback from system Minimal user input Flexibility Good visual appearance Close match to tasks of user

General

Application specific

Consistency

what is about car design which lets people transfer driving skills between different makes of car?

keeping key design features consistent (type of steering control, arrangement of pedals, operation of gears)

still permits individual styling of cars consistency doesn't mean all cars look the same list 4 features associated with the 'drivability' of

graphical interfaces

Consistency Commands

usage of command names standard key bindings

e.g. ESC always cancels previous command

F1 always displays help screen syntax

Format for data entry Layout

consistent use of screen areas so the user knows where to look

for instructions, error messages and status information. Information coding

colour highlighting

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.22 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

44.32 33.60 62.86 55.31 15.21 12.31

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.22 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

44.32 33.60 62.86 55.31 15.21 12.31

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.28 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

Screen from Currency Trading Information System

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.22 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

44.32 33.60 62.86 55.31 15.21 12.31

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.22 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

44.32 33.60 62.86 55.31 15.21 12.31

23.34 34.43 23.56 56.76 12.23 12.73

45.76 38.22 63.78 56.66 14.53 11.53

46.77 32.78 62.88 56.66 15.76 11.87

Another Screen from Same Currency Trading Information System

Consistency

Inconsistency is reduced by: definition of and adherence to

agreed style and standards use of software structures which

encourage global definition of interface characteristics

Appropriate user support

HELP messages important to recognise different types of help; should be available when required and context-specific; can the user get help about what responses are possible at a

given point in a dialogue. ERROR messages

should explain what is wrong and what corrective action is required;

should use ‘jargon’ familiar to the user; often this support is poorly designed in terms of what information

is given to the user.

Feedback from the system

Every action the user makes should produce a perceptible response.

Response time for feedback should be appropriate to the type of user action: e.g. response to keystroke - instantaneous;

response to command input - may take longer. Current object should be highlighted:

window;

icon or graphic object. Provide ‘system busy’ feedback if time will exceed a few

seconds or is unpredictable.

Feedback from the system

Provide indication of how many transactions remain, for example as a bar chart or as a percentage.

The intention is to reduce user uncertainty that the system has: received the last input, is currently doing something about it, or is waiting for the next input.

Minimal user input Balance between number of keystrokes or mouse

movements/clicks and memory load. Reducing keying errors increases speed of data

entry. Allow selection from a list rather than typing in a

value (recognise rather than recall). Edit a command that has produced an error rather

than retyping the command. Do not request input of information which can be

derived automatically or which has been entered previously.

Use default values.

Flexibility

Measure of how well a dialogue can cater for different levels of user skill.

Provide alternative means of achieving the same goal which match different models of how the interface works. e.g. word selection: cursor to start of word and

double click, click and drag, click and shift-click. e.g. word deletion: word highlighted and Control +X

key, select ‘Cut’ menu option, backspace.

Flexibility

Adapt to the skill level of the user by: providing accelerators:

allow user to answer ahead,provide key bindings for menu options;

providing macro facility; accepting abbreviations for command words; accepting synonyms (alternative names); allowing user to choose level of instructions or

help.

Heuristics (after Shneiderman)

strive for consistency enable frequent users to use shortcuts offer informative feedback design dialogues to yield closure offer simple error handling permit easy reversal of actions support internal locus of control reduce short term memory load

Heuristics (after Neilsen)

use simple and natural dialogue speak the users language minimize user memory load be consistent provide feedback provide clearly marked exits provide shortcuts provide good error messages prevent errors

Windows Interface Guidelines

directness user in control consistency

forgiveness feedback aesthetics simplicity

• set of general principles for interface design in Microsoft's software development documentation

Directness (after Microsoft)

allow users to directly manipulate software representations of information.

users should see how the actions they take affect the objects on the screen.

Visibility of information and choices also reduce the user's mental workload.

Users can recognize a command easier than they can recall its syntax.

User in control (after Microsoft)

user initiates actions, not the computer or software

use techniques to automate tasks, but implement them in a way that allows the user to chose or control the automation.

users must be able to personalize aspects of the interface, such as color, fonts, or other options

Consistency (after Microsoft)

allows users to transfer existing knowledge to new tasks and focus more on tasks because they need not spend time trying to remember the differences in interaction.

makes the interface familiar and predictable. by providing a sense of stability

important through all aspects of the interface, names of commands, visual presentation of information, and operational behavior.

Forgiveness (after Microsoft)

Users like to explore an interface and often learn by trial and error.

An effective interface allows for interactive discovery.

It provides only appropriate sets of choices and warns users about potential situations where they may damage the system or data, or better, makes actions reversible or recoverable.

Feedback (after Microsoft)

Always provide feedback for a user's actions.

Visual, and sometimes audio, cues should be

presented with every user interaction to confirm that the software is responding to the user's input and to communicate details that distinguish the nature of the action.

Aesthetics (after Microsoft)

visual design is an important part of a software's interface.

important to remember that every visual element that appears on the screen potentially competes for the user's attention.

Provide a pleasant environment that clearly contributes to the user's understanding of the information presented.

Simplicity (after Microsoft)

An interface should be simple (not simplistic), easy to learn, and easy to use.

It must also provide access to all functionality provided by an application.

Maximizing functionality and maintaining simplicity work against each other in the interface.

An effective design balances these objectives.

Summary Human-computer dialogues can be viewed as an

exchange of messages or the user changing the state of application objects.

Dialogues can be designed to assist the user through: Consistency Support Feedback Minimal input Flexibility

Several similar lists of good design principles

For next week....

Make sure you have read Preece, Chapter 13.