2. Design Goal
“Every designer wants to build a high quality
interactive system that is admired by colleagues,
celebrated by users, circulated widely, and
imitated frequently.”
-Shneiderman,
4. Details
Useful: Your content should be original and fulfill a need
Usable: Site must be easy to use
Desirable: Image, identity, brand, and other design
elements are used to evoke emotion and appreciation
Findable: Content needs to be navigable and locatable
onsite and offsite
Accessible: Content needs to be accessible to people
with disabilities
Credible: Users must trust and believe what you tell them
6. Define Usability
Usability is a quality attribute that assesses
how easy user interfaces are to use. The word
"usability" also refers to methods for improving
ease-of-use during the design process.
11. Synthesizability
Synthesizability: support for the user to assess the
effect of past operations on the current state (can I
‘tell’ why I am here based on what I have gone
through in the past?).
12. Familiarity
Familiarity: the extent to which a user's
knowledge and experience in other real-world or
computer-based domains can be applied when
interacting with a new system.
13. Generalizability
support for the user to extend knowledge of
specific interaction within and across applications
to other similar situations.
14. Consistency
likeness in input-output behaviour arising from
similar situations or similar task objectives.
17. Dialogue initiative
user freedom from artificial
constraints on the input
dialog imposed by the
system; user vs system -
who has the initiative in the
dialog?
19. Task Migratability
the ability to transfer control for execution of tasks
between the system and the user (consider e.g.,
spell-checking task).
20. Substitutivity
:the extent to which an application allows
equivalent input and output values to be
substituted for each other (values in input eg
fractions/decimals, values in output eg both
digital and analog, output/input eg output can be
reused as input).
21. Customizability
the ability of the user or the system to modify
the user interface. (adaptability vs adaptivity) ?-
initiated modification.
22. Robustness
The level of support provided to
the user in determining successful
achievement and assessment of
goal-directed behaviour.
27. Task conformance
the extent to which the system services support all
the tasks the user would wish to perform and in
the way the user would wish to perform.
29. We can consider TWO sets
here (Already Studied)
Shneiderman’s Eight Golden Rules of
Interface Design
Norman’s Seven Principles for
Transforming Task into Simple Ones
30. Ben Shneiderman's 8 Golden
Rules
1. Strive for consistency: layout, terminology, command usage, etc.
2. Cater for universal usability: recognize the requirements of diverse users and
technology. For instance add features for novices eg explanations, support
expert users eg shortcuts.
3. Offer informative feedback: for every user action, offer relevant feedback and
information, keep the user appropriately informed, human-computer interaction.
4. Design dialogs to yield closure: help the user know when they have
completed a task.
5. Offer error prevention and simple error handling: prevention and (clear and
informative guidance to) recovery; error management.
6. Permit easy reversal of actions: to relieve anxiety and encourage exploration,
because the user knows s/he can always go back to previous states.
7. Support internal locus of control: make the user feel that s/he is in control of
the system, which reponds to his/her instructions/commands. 8. Reduce short-
term memory load: make menus and UI elements/items visible, easily
available/retrievable, ...
31. [Donald] Norman's 7
Principles
1. Use both knowledge in the world and knowledge in the head.
2. Simplify the structure of tasks.
3. Make things visible: bridge the gulfs of Execution and Evaluation.
4. Get the mappings right.
5. Exploit the power of constraints, both natural and artificial.
6. Design for error.
7. When all else fails, standardize.
32. Some more …Heuristics to
measure Usability
1. Visibility of system status
2. Match between system and the real world
3. User control and freedom
4. Consistency and standards
5. Error prevention
6. Recognition rather than recall
7. Flexibility and efficiency of use
8. Aesthetic and minimalist design
9. Help users recognize, diagnose, and recover from errors
10. Help and documentation
33. Some more …Heuristics to
measure Usability
Visibility of system status The system should always keep
users informed about what is going on, through appropriate
feedback within reasonable time.
Match between system and the real world The system
should speak the users' language, with words, phrases and
concepts familiar to the user, rather than system-oriented
terms. Follow real-world conventions, making information
appear in a natural and logical order.
User control and freedom Users often choose system
functions by mistake and will need a clearly marked
"emergency exit" to leave the unwanted state without having
to go through an extended dialogue. Support undo and
34. 10 important Heuristics to
measure Usability
Consistency and standards Users should not have to
wonder whether different words, situations, or actions mean
the same thing. Follow platform conventions.
Error prevention Even better than good error messages is
a careful design which prevents a problem from occurring in
the first place. Either eliminate error-prone conditions or
check for them and present users with a confirmation option
before they commit to the action.
Recognition rather than recall Minimize the user's
memory load by making objects, actions, and options
visible. The user should not have to remember information
from one part of the dialogue to another. Instructions for use
35. Some more …Heuristics to
measure Usability
Flexibility and efficiency of use Accelerators -- unseen
by the novice user -- may often speed up the interaction for
the expert user such that the system can cater to both
inexperienced and experienced users. Allow users to tailor
frequent actions.
Aesthetic and minimalist design Dialogues should not
contain information which is irrelevant or rarely needed.
Every extra unit of information in a dialogue competes with
the relevant units of information and diminishes their relative
visibility.
36. Some more …Heuristics to
measure Usability
Help users recognize, diagnose, and recover from
errors Error messages should be expressed in plain
language (no codes), precisely indicate the problem, and
constructively suggest a solution.
Help and documentation Even though it is better if the
system can be used without documentation, it may be
necessary to provide help and documentation. Any such
information should be easy to search, focused on the user's
task, list concrete steps to be carried out, and not be too
large.
38. How to Improve Usability
There are many methods for studying usability, but the most
basic and useful is user testing, which has 3 components:
Get hold of some representative users, such as customers for
an e-commerce site or employees for an intranet (in the latter
case, they should work outside your department).
Ask the users to perform representative tasks with the design.
Observe what the users do, where they succeed, and where they
have difficulties with the user interface. And let the users do the
talking.
39. Points to remember while
going for Usability
It's important to test users individually and let them solve
any problems on their own. If you help them or direct their
attention to any particular part of the screen, you have
contaminated the test results.
To identify a design's most important usability problems by:
testing 5 users is typically enough.
Rather than run a big, expensive study, it's a better use of
resources to run many small tests and revise the design
between each one so you can fix the usability flaws as you
identify them.
User testing is different from focus groups, which are a poor
way of evaluating design usability.
Iterative Design
40.
41. When to work on Usability
Before starting the new design, test the old design to
identify the good parts that you should keep or emphasize,
and the bad parts that give users trouble.
Unless you're working on an intranet, test your
competitors' designs to get cheap data on a range of
alternative interfaces that have similar features to your
own.
Conduct a field study to see how users behave in their
natural habitat.
42. When to work on Usability
Make paper prototypes of one or more new design ideas
and test them. The less time you invest in these design
ideas the better, because you'll need to change them all
based on the test results.
Refine the design ideas that test best through multiple
iterations, gradually moving from low-fidelity prototyping
to high-fidelity representations that run on the computer.
Test each iteration.
Inspect the design relative to established usability
guidelines whether from your own earlier studies or
published research.
Once you decide on and implement the final design, test
it again. Subtle usability problems always creep in during
43. Need of guidelines
As the theories underlying HCI design are difficult to
produce specific standard so most of the design rules are
based on general guidelines
Well-known guidelines include the Apple Human
Interface Guidelines, Java Look and Feel Design Guidelines,
and Java Look and Feel Graphics Repository
44. Guidelines: Organization
High-level goals for data display organization
(Smith and Mosier 1986)
1. Consistency of data display
2. Efficient information assimilation by the user
3. Minimal memory load on the user
4. Compatibility of data display with data entry
5. Flexibility for user control of data display
45. Guidelines Navigation
National Cancer Institute has published a 388-
guideline
set for Web pages:
• “Standardize task sequences”
• “Ensure that embedded links are descriptive”
• “Use unique and descriptive headings”
• “Use check boxes for binary choices”
• “Develop pages that will print properly”
• “Use thumbnail images to preview larger
images”
46. Guidelines for Accessibility
World Wide Web Consortium (W3C), adapted from
US Rehabilitation Act Amendments of 1998
“Provide a text equivalent for every non-text
element”
“For any time-based multimedia presentation,
synchronize equivalent [non-multimedia] alternatives”
“Ensure that all information conveyed with color is
also available without color”
“Provide a title for every Web frame”
47. Display Guidelines may be
Application- or Domain-Specific
…but in the end they share
common themes — case in point, a
Lockheed set for electric-power
control rooms
48. Display Guidelines
Be consistent in labeling and graphic conventions
• Standardize abbreviations
• Use consistent formatting in all displays
• Present data only if they assist the operator
• Avoid alphanumeric data when possible
• Present alphanumeric data only when necessary
• Use and maintain high-resolution monitors
• Design in monochrome first, then add color only where
needed
• Involve users when developing new displays and
procedures
49. Guidelines: Notification
Wickens and Hollands have proposed techniques
for making information stand out (2000):
intensity inverse video
marking blinking
size color
fonts audio
Caveat Notificator!
50. Cautions Notificator!
Notification is an area where tradeoffs may
occur:
attention-grabbing techniques may “dull” the
user’s awareness…or, at the very least, irritate
or annoy the user
Similar formatting implies relationships among
similarly formatted items
Sound saves display real estate, and is
processed differently by the brain — but, like
visual attention grabbers, must not be overdone
51. Guidelines: Input/Data Entry
Proper data entry is crucial in some areas — many
times, bad data entry results in serious consequences
Enter Smith and Mosier again, with these goals:
1. Consistency in data-entry transactions
2. Minimal input actions by user
3. Minimal memory load on users
4. Compatibility between data entry and display
5. Flexibility for user control of data entry
User control vs. consistency — a frequent tradeoff
