UI Guidelines 1

Adapted from: The Human Factor: Designing Computer Systems for

People, Rubinstein & Hersh (1984)

Know your users - they are not you

How long does it take to learn the system (novice ... expert curve)

Ease of use must be designed in, not added

Reliable & robust

absence of malfunctions

tolerance of errors

protect user from harmful actions

Designers make myths.

Users make conceptual models.

User Interface Guidelines

UI Guidelines 2

Tailoring: accommodate individual differences w/o users having to make

choices at every function. (Training wheels, user models)

Productivity: using a computer should always be easier than not using a

computer.

Planning pays for itself many times!

Software Engineering is compromise. Integrated design is design of a

whole system.

Separate Design from Implementation

Use prototypes - evolutionary delivery to test design.

Quality requires planning. Quality control is not just testing!

Quality is measuring the fit of design goals to system functionality.

Can you design what you can't measure?

UI Guidelines 3

20 / 80 rule Law of diminishing returns...

Creeping elegance - last 20% of "perfectly complete" system takes

80% of the effort.

80 / 20 rule Put your effort where main impact will be.

20% of an application's code may do 80% of the user interface.

Who is the user? Meet the user.

What tasks does the user perform now?

Watch the user perform tasks.

Describe Before you Leap

Task Analysis and User Models

UI Guidelines 4

How is the task learned? Learn the task.

Where is the task performed? Perform task.

What is the relationship between user and data?

What other tools does the user have?

How do users communicate w/ each other?

What are the task's time constraints?

How do things go wrong?

What happens when things go wrong?

What work around exist?

How do user currently recover?

Develop an explicit use model consistent with task.

Know the task!

Task

UI Guidelines 5

Maintain a consisent myth.

Complete, Limited Scope Systems.

Have clear bounds that user can understand

Visible & Distinguishable System's States .

Minimize Conceptual Load.

Recognize human processing limits

Eliminate Mode Errors

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no rules many

independent termsmany

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Develop & Use Conceptual Models

UI Guidelines 6

Respect the Rules of Human Conversation

When people use language to interact w/ a computer they behave as if

the rules of human - to - human communication apply.

Respond with the Appropriate Amount and Type of Information.

Data is information w/o interpretation.

People are information not data processors!

Numerical Information:

Exact data is important - use tables

Relationships are important - use graphs

Dimensionality should fit the data -- 3D graphs confusing

Present what is needed, not all there is

Language && Relationships

UI Guidelines 7

The system doesn't understand the user

don't condemn user - avoid "error"

Incorporate spelling correctors -- minimize free text entry

recognize - select > recall - generate

Be Consistent in Language Use.

Consistent word, grammar and style

Don't anthropomorphize dialog w/ user -- wrong model of system to user

System is a tool not a "friend"

System should be transparent to task

The User is Always Right

UI Guidelines 8

Avoid teaching command grammars, teach command syntax through use

(intuitive).

Native language is learned by using and example, not by syntax and

grammar.

Use Application Terminology& Standard Language.

Eliminate vague, poor terms.

Make and use relevant metaphors

Avoid complex queries.

Ands can be exhaustively sequenced

Ors can be sequenced w/ priority

Teach by example, not by Formalisms.

UI Guidelines 9

Learning Aids are Part of the System

Training Wheels - teaching software that can be removed latter.

Tutorials designed & developed w/ system

Write the User's Guide First

Incorporate external myths into guide

Organize on conceptual model

Examples, examples, examples...

An index is an Information Retrieval System

Expand the Definition of Software

UI Guidelines 10

Help should not interfere w/ task

Multiple levels of help

1 show example

2 provide "manual pages" (hyper text)

3 refer user to integrated tutorials

4 refer user to human instructors or

consultants

DWIM "do what I mean"

Guess what user wants and query if they want it.

Then provide correct example (a training wheel).

Prove that Help Helps

Integrate help w/ error processing

Help should help

UI Guidelines 11

Avoid Multiple Style Models - Consistent UI

Command Based Interface Style

Punctuation shouldn't have meaning

Have command line recall & editing

Menu Based Interface Style

Keep menus short

Label menus

Have consistent menu operations

If large menu, have menu map (history path) & shortcuts

Human Interface Styles

UI Guidelines 12

Direct Manipulation Interface Styles

Respond in real time

Match objects in interface w/ external myth

Reduce homing between keyboard & pointer - provide keyboard

accelerators

Respond to Users

Provide High Quality, Timely Response

Keep users informed and comfortable

have progress indicators for long tasks

Acknowledge user's actions, then process

Confirm user's intent not literal string.

Provide easy escape, undo features

UI Guidelines 13

No surprises, don't distract.

Report errors politely, simply, and in context

State errors in terms of external myth

Don't blame the user

Avoid error codes. Error messages should be unambiguous.

Fix the problem (DWIM - training wheels)

Clearly distinguish between success & error

Design the Error & Help Behavior of System from the beginning

Handle Errors to Teach & be Productive

Error Response

UI Guidelines 14

Response Time should be Fast and Relatively Constant

Try to work in real time

Have progress indicators, percent done, announce long delays, estimate

how long task will take

Response time is part of user's perception.

Try to have response time and duration support external myth.

Should "hard" tasks should take a little longer ?

Integrate error recovery & help

UI Guidelines 15

You build it, You Test it ? You buiild it, others test it? Both ?

Specify testing & validation at design time. Have external testers also.

Use subjects that are familiar w/ system or external myth (not other

developers)

Test User Interface w/ prototypes from screen "demo" mock-ups

use representative tasks

include help and error recovery

Test the strength of the external myth

Use an evolutionary (rapid prototyping) design w/ many deliveries

exploit reusable code, object oriented tools

Failures are Catastrophes not "cute" bugs....

Testing Systems

UI Guidelines 16Design as a reflection

Design Model User Model

designer user

ideal system

actual system

Design Model User Model

designer user

UI Guidelines 17

Assume 3 competitive applications (A, B, and C) that exhibit these

performance as a function of use functions.p

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learning and use

A

B

C

"A" is the fastest to learn and the fastest to asymptote at a moderate level

of performance.

"B" is slow to learn and slow to asymptote at a low level of performance.

"C" is slow to learn and slow to asymptote at a high level of

performance.

Are there user's appropriate for each application?

Humans learn

UI Guidelines 18

Studies supporting consistency examine ease of learning and ease of

transference from one system to another.

Internal consistency reduces conceptual load

External consistency reduces training

Assumes that easy to learn is easy to use...

However,

Humans are fast learners, but learning is “hard”

Systems are acquired to use for increased productivity

not for learning

Skilled performance is important, may require learning

Training Wheels, incorporate learning into beginning user model,

monitor performance and remove “training wheels” from UI

learning is not using

UI Guidelines 19

J. Grudin, CACM, 1989

Consistency is a major watch word in guides for developing good user

interfaces.

Consistency != perceived consistency

3 Types of Consistency

1. Internal Consistency. Easily controlled by the design team.

Command language

2. User Interface Consistency. Externally consistent with environment

or desktop. -- User Interface controls menus, buttons, dialogs ...

3. Tool / Analogy Consistency. Consistent with a model, analogy, or

external tool. -- Remote monitoring & physical gauges

Case against Interface Consistency

UI Guidelines 20

Intensive task use analysis of users is vital to user interface design.

Consistency can be centered on:

• what is most often done

• what did the user do last

• what would the user do next

Grudin's Arrow Keys

12 3

Which is better?

1 more consistent with external analogy

- correction is opposite key

2 best performance

+ easy correction, multi-fingered use

Consistency is One of Many Goals

UI Guidelines 21Thinking Fast & Slow

Two cognitive human decision making systems:

System 1: automatic, unconscious, approximate, easy, visual,

emotional / sensational, fast

System 2: conscious, deliberate, rational, precise, difficult, verbal,

slow

Most decisions are made with system 1 (default system)

Important decisions should be made with system 2.

Tversky & Kahneman, Judgment under Uncertainty: Heuristics and

Biases, 1974

Psychology of decision making

Behavioral Finance

Losses > Gains risk averse but like to gamble and take risks

Sensational, Memorial > Statistics, Factual

fears flying, prefers to drive

good story, familiar source rather that facts

UI Guidelines 22System 2 applications

Decision Support Systems (DSS) – tools for System 2

Provide “all” options. But don’t overwhelm, organize options,

provide summary “thumbnails” information

Facilitate alternatives. Expose users to non-intuitive alternatives,

help discovery of decisions.

Information based. Provide unbiased data w/o requirement for

calculation. Perform deductions (show steps if asked), provide

inferences. (minimize system 2.)

Transparent working. Explain assumptions and results with

examples, memorial stories. (play to system 1.)

UI Guidelines 23System 1 applications

Persuasive applications – sweets for System 1

Make a quick, impulsive, self-satisfying decision

Charities, Advertisers, Political/religious recruiters

Visual, emotional images: fear, pleasure, status

Exploiting System 1 for the “greater good”

How to increase system updates, backups, redundant storage?