1. (Introduction, Part 2) Fall 2008
CS305, HCI in Software Development Usability Goals, Principles, Guidelines
(Introduction, Part 2)
Fall 2008

2. Activity (Mini-Homework)
Do this on your own on in pairs
Go find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)
Problem must illustrate a violation of one of the design principles or usability guidelines
Describe the problems in these terms
“Post” on Collab wiki page before class next Fri.

3. Reminder….
users should be involved through the development of the project
specific usability and user experience goals need to be identified, clearly documented and agreed at the beginning of the project
iteration is needed through the core activities

4. Towards More Usable Systems
Seems like we need the following:
Goals we want to achieve
Principles on how to achieve these
Lists of do’s and don’ts
Theories that underlie principles, lists
Methods for measuring and evaluating

5. Usability Goals Here’s one set (from the ID textbook) Effective to use
Efficient to use
Safe to use
Have good utility
Easy to learn
Easy to remember how to use

6. Usability Goals Effective to use (effectiveness)
A general goal: how well does a system do what it should do?
Efficient to use (efficiency)
Do things quickly, easily.
Especially common tasks.
Safe to use (safety)
Protect people from hazards (usually not a SW issue)
Help prevent user from making errors and recover from errors
Give users confidence

7. Usability Goals (2) Have good utility Easy to learn (learnability)
Has the right kind of functionality
Supports users in accomplishing tasks
Easy to learn (learnability)
Includes how easy it is to learn advanced features. (If hard, who bothers?)
Easy to remember how to use (memorability)
Many systems used infrequently

8. How to Measure Usability?
We want to achieve these goals, but how do we know?
Develop measurable criteria based on previous goals. Examples:
Time to learn
Speed of performance
Rate of errors over by users
Retention over time
Subjective satisfaction

9. User experience goals Satisfying - rewarding Fun - support creativity
Enjoyable - emotionally fulfilling
Entertaining …and more
Helpful
Motivating
Aesthetically pleasing

10. Usability and user experience goals
How do usability goals differ from user experience goals?
How easy is it to measure usability versus user experience goals?
Are there trade-offs between the two kinds of goals?
e.g. can a product be both fun and safe?

12. Reminder of where we are
Usability Goals
Some measures
User Experience Goals
Design Principles
First two were higher level (goals)
Now talking about guidance for how to achieve goals
Guidelines (guidance as lists)

13. Design principles
Generalizable abstractions for thinking about different aspects of design
The do’s and don’ts of interaction design
But at a high level. (Compare to guidelines later.)
What to provide and what not to provide at the interface
Derived from a mix of theory-based knowledge, experience and common-sense

14. Higher-level Principles
Now, we’ll talk about the following:
Visibility
Feedback
Constraints
Mapping
Consistency
Affordances
Ideas well-known (e.g. from Norman’s Design of Everyday Things)

15. Activity (Mini-Homework)
Do this on your own on in pairs
Go find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)
Problem must illustrate a violation of one of the design principles or usability guidelines
Describe the problems in these terms
“Post” on Collab wiki page before class next Fri.

16. Visibility • This is a control panel for an elevator.
• How does it work?
• Push a button for the floor you want?
• Nothing happens. Push any other button? Still nothing. What do you need to do?
It is not visible as to what to do!
From:

17. Visibility
…you need to insert your room card in the slot by the buttons to get the elevator to work!
How would you make this action more visible?
make the card reader more obvious
provide an auditory message, that says what to do (which language?)
provide a big label next to the card reader that flashes when someone enters
make relevant parts visible
make what has to be done obvious

18. Feedback Sending information back to the user about what has been done
Includes sound, highlighting, animation and combinations of these
e.g. when screen button clicked on provides sound or red highlight feedback:
“ccclichhk”

19. Constraints Restricting the possible actions that can be performed
Helps prevent user from selecting incorrect options
Three main types (Norman, 1999)
physical
cultural
logical

20. Physical constraints
Refer to the way physical objects restrict the movement of things
E.g. only one way you can insert a key into a lock
How many ways can you insert a CD or DVD disk into a computer?
How physically constraining is this action?
How does it differ from the insertion of a floppy disk into a computer?

21. Logical constraints
Exploits people’s everyday common sense reasoning about the way the world works
An example is the logical relationship between physical layout of a device and the way it works
See next slide for an illustration

22. Logical or ambiguous design?
Where do you plug the mouse?
Where do you plug the keyboard?
top or bottom connector?
Do the color coded icons help?
From:

23. More Logically Constrained
Provides direct adjacent mapping between icon and connector
Provides color coding to associate the connectors with the labels
From:

24. Cultural constraints
Learned arbitrary conventions like red triangles for warning
Can be universal or culturally specific
For SW we’ve accepted certain conventions, e.g. we know what to do with an icon
Be concerned of cross-cultural conventions and other ambiguities!
Does an “X” mean “selected” or “not selected”
Is a check-mark better?

25. Which are universal and which are culturally-specific?

26. Mapping
Relationship between controls and their movements and the results in the world
Why is this a poor mapping of control buttons?

27. Mapping Why is this a better mapping?
The control buttons are mapped better onto the sequence of actions of fast rewind, rewind, play and fast forward
Is this a logical mapping (in most people’s minds)?
Is there a mapping that makes more sense?

28. Mappings in the Kitchen
Which controls go with which rings (burners)? A B C D

29. Why is this a better design?

30. Consistency
Design interfaces to have similar operations and use similar elements for similar tasks
For example:
always use ctrl key plus first initial of the command for an operation – ctrl+C, ctrl+S, ctrl+O
Main benefit is consistent interfaces are easier to learn and use
But… didn’t a wise man say this? Consistency is the hobgoblin of little minds.
A foolish consistency is the hobgoblin of little minds (adored by little statesmen and philosophers and divines)
Quote from Ralph Waldo Emerson, Self-Reliance

31. When consistency breaks down
What happens if there is more than one command starting with the same letter?
e.g. save, spelling, select, style
Have to find other initials or combinations of keys, thereby breaking the consistency rule
E.g. ctrl+S, ctrl+Sp, ctrl+shift+L
Is this desirable? Does it defeat the purpose?
It may increase learning burden on user
It may make them more prone to errors
But it may still benefit frequent or experienced users

32. Internal and external consistency
Internal consistency refers to designing operations to behave the same within an application
Difficult to achieve with complex interfaces
External consistency refers to designing operations, interfaces, etc., to be the same across applications and devices
Very rarely the case, based on different designer’s preference
Most successful in product families (e.g MS Office)
Op. Sys. vendors may define style guidelines

33. Keypad numbers layout A case of external inconsistency
(a) phones, remote controls
(b) calculators, computer keypads 1 2 3 7 8 9 4 5 6 4 5 6 7 8 9 1 2 3

34. Affordances: to give a clue
Refers to an attribute of an object that allows people to know how to use it
E.g. a mouse button invites pushing, a door handle affords pulling
Norman (1988) used the term to discuss the design of everyday objects
Since then has been popularized in interaction design to discuss how to design interface objects
E.g. scrollbars to afford moving up and down, icons to afford clicking on

35. What does ‘affordance’ have to offer interaction design?
Notion of affordance is often over-used!
Interfaces are virtual and do not have affordances like physical objects
Norman argues it does not make sense to talk about interfaces in terms of ‘real’ affordances
Instead interfaces are better conceptualised as ‘perceived’ affordances
Learned conventions of arbitrary mappings between action and effect at the interface
Some mappings are better than others

36. Activity 1.3 Physical affordances:
How do the following physical objects afford? Are they obvious?

37. Activity 1.4 Virtual affordances
How do the following screen objects afford?
What if you were a novice user?
Would you know what to do with them?

38. Activity 1.5: Physical and Perceived Affordances
Take a cell phone, digital camera, or PDA
Have laptop? Open a fancy SW app: Outlook, Eclipse, etc?
In a small group
Identify any physical affordances the device has
Identify any perceived or visual affordances the software user interface has
Write these down, be prepared to share or turn in

39. A Good Example
Kodak DC-290 digital camera

40. Adjusting Tabs in MS Word
What’s the idea here? Problems?
What principle(s)?
Affordance
Metaphor (more on this later)

41. Web Links What are the conventions that help you recognize a link?
Would you are argue this is an affordance?
A perceived affordance – convention of a mapping between action and effect
Does it “afford” clicking on it?
Examples of problems with this?
Let’s look at:
Underline is the convention.
Changes color when hover over
changes after visited
Also graphics images (sometimes)
Sometimes not underlined
Bold text (but not all bold)
Sometimes buttons

44. Overview (Reminder) Guidelines Usability Goals User Experience Goals
Design Principles
Guidelines
Still talking about guidance for how to achieve goals
These are more prescriptive (do’s & don’ts)

45. Guidelines What do we mean by “guidelines”?
Tell me!
Are guidelines enough? Lead to problems?
Too specific, incomplete. Don’t generalize to all situations
But… Capture experience and best practices
Many examples of guidelines…

46. Nature of Guidelines
Similar to design principles, except more prescriptive
Used mainly as the basis for evaluating systems
Provide a framework for heuristic evaluation
We’ll talk about particular approach to evaluation this later

47. Jakob Nielsen Says… Jakob Nielsen: a leading figure in usability
Member of the Nielsen Norman Group
Donald Norman
Bruce "Tog" Tognazzini
Alertbox: regular “column”
Wikipedia:

48. “Usability principles” (Nielsen 2001)
Visibility of system status
Match between system and the real world
User control and freedom
Consistency and standards
Help users recognize, diagnose and recover from errors
Error prevention
Recognition rather than recall
Flexibility and efficiency of use
Aesthetic and minimalist design
Help and documentation

49. Read More about Nielsen’s List(s)
Nielsen’s site has more on the previous list
Heuristics: more general “guidelines”
We’ll see this term again
Heuristic evaluation
Activity 1.7 for you to do:
Find one list of similar usability principles (i.e heuristics, prescriptive guidelines, do’s/don’ts) for Web page design
Write it down – we’ll collect these

50. Shneiderman’s Eight Golden Rules
Strive for consistency
Cater to universal usability
Offer informative feedback
Design dialogs to yield closure
Prevent errors
Permit easy reversal of actions
Support internal locus of control
Reduce short-term memory load.

51. More Specific Guideline Examples from DTUI
Shneiderman’s text (DTUI) gives some more detailed examples
National Cancer Institute, p. 62
W3C, Accessibility, p. 62
Display organization, p. 63
Control rooms, p. 63
Others in Section 2.2
Ask yourself: what principle(s) underlie each guideline?

52. Ex. 1: National Cancer Institute
388 guidelines for informative web pages, such as:
Reduce user’s workload
Do not display unsolicited windows or graphics
Standardize task sequences
Ensure embedded links are descriptive
Use unique and descriptive headings
Develop pages that print properly
Use thumbnail images to preview large images

53. Ex. 2a, Organizing Data Display
From Smith and Mozier (1986).
Data display: 5 high-level goals
Consistency of data display
Efficient information assimilation by the user
Minimal memory load on the user
Compatibility of data display with data entry
Flexibility for user control of data display
Data entry: 5 similar high-level goals, but also:
Minimal input actions by user

54. Ex. 2b, More Specific than 2a
Lockheed (1981) on control rooms
Be consistent in labeling, graphics, formatting
Standardize abbreviations
Present data only if it assists the operator
Present data graphically where appropriate instead of numbers and text
Rely on monochromatic displays with good spacing and arrangement, saving color for when it helps
Involve users in development of displays

56. Activity (Mini-Homework)
Do this on your own on in pairs
Go find two examples of problems in the GUIs of software apps or the UI of a interactive device (not Web pages)
Problem must illustrate a violation of one of the design principles or usability guidelines
Describe the problems in these terms
“Post” on Collab wiki page before class next Fri.