Upload
portia-suarez
View
36
Download
1
Embed Size (px)
DESCRIPTION
Designing Usable Systems. This course should enable you to design and implement better user interfaces We will look at case studies in Web browsing Cellular Telephones VCR’s Programming Languages. Why are you here?. Because I needed the credits. Why am I here?. - PowerPoint PPT Presentation
Citation preview
Gary Marsden Slide 1University of Cape Town
Designing Usable Systems
This course should enable you to design and implement better user interfaces
We will look at case studies in– Web browsing– Cellular Telephones– VCR’s– Programming Languages
Gary Marsden Slide 2University of Cape Town
Why are you here?
Because I needed the credits
Gary Marsden Slide 3University of Cape Town
Why am I here?
Because I’m paid to be here…
Gary Marsden Slide 4University of Cape Town
What do we know?
– HTML– Tcl– Java– Graph Theory– State Transition Diagrams / Finite State
Automata– State Charts (Harel)
Gary Marsden Slide 5University of Cape Town
Course Assessment
Two parts– Evaluation of usability
• Due soonish
– Analysis of a gadget• Presentation • Analysis• Simulation
Gary Marsden Slide 6University of Cape Town
Reading list
No set text– Handouts– P.O.E.T - Don Norman– State charts - best book is Ian Horrocks– My book
Gary Marsden Slide 7University of Cape Town
Course in a nutshell
Here are some assumptions I am working on, and will give you an idea where I am coming from– Gadgets and software are badly designed and
everyone accepts this as normal* (Dilbert)– HCI does little to help programmers engineer
usable systems– Most HCI is post disaster finger wagging and
relies on there being an artefact to evaluate
This is a slight rant, but I am happy to discuss any point with you.
Gary Marsden Slide 8University of Cape Town
Usability - does it exist?
Before we can look at usability, we have to look at how it is currently perceived
To do this, we need to analyse how users know that a product is ‘usable’
This is not as easy as it sounds. A good place to start looking is by analysing the tasks products are designed to solve.
Gary Marsden Slide 9University of Cape Town
Task types - external
For some products, it is easy to see how well they fulfil their role:– chair, car, hi-fi, television
This type of product is designed to fulfil some need that exists in the physical world.
This type of task we shall call “external” and is not interesting to our discussion.
Gary Marsden Slide 10University of Cape Town
Task types - internal
The other type of task is an “internal” task.
Here a device is built to solve a problem which exists only because the device exists!
With these internal tasks, the problem is defined in terms of the device created to solve the problem – this makes assessing task performance incredibly difficult.
Gary Marsden Slide 11University of Cape Town
Visibility - Physical and DM
Another problem in assessing usability is the lack of visibility in electronic devices
Physical devices have visible qualities which we can assess
Software can be visible (Direct Manipulation) but also invisible (DOS)
Electronics have physical attributes which are not worth investigating
Gary Marsden Slide 12University of Cape Town
Direct Manipulation (Ben Shneiderman)
From studies on video games, decided that:– Users should see objects – Objects should be controlled directly– State is always visible
This led to interfaces such as the Star, Lisa and Macintosh
Gary Marsden Slide 13University of Cape Town
Visibility - gadget
Direct manipulation has helped with software, but most computers are sold in embedded systems
Cellular handsets etc. have limited interfaces
This was OK when processors were under powered, not acceptable now
Gary Marsden Slide 14University of Cape Town
Masochism
Before we go on to look at usable systems, it is worth mentioning that some people like unusable systems
– Computer games rely on having obscure interfaces
– The World Wide Web it is fun to just surf around hoping to bump into something interesting
Gary Marsden Slide 15University of Cape Town
Introducing usability to products
I hope I have convinced you in the first lecturer that devices are not as usable as they might be
One possible explanation for this is that the technology is not mature enough yet to allow usability it to develop
Gary Marsden Slide 16University of Cape Town
Mature technology
Let us switch briefly to an more mature technology as a case study: cars– Originally sold on the fact they worked– Later came technologies (“Balanced Power”)– Ultimately came safety and usability
• Ralph Nader changed perception of this
Gary Marsden Slide 17University of Cape Town
Electronic maturity
So is the electronic industry in a mature state?
To answer this we need to look at Christensen’s ideas (MIT professor looking at “disruptive” technology
l
t
He assumes that technology develops over time and eventually reaches some level where it is sufficient for a taskThis is true for “external” tasks
Gary Marsden Slide 18University of Cape Town
Internal task maturity
This time, the graph looks a little different
The curve never meets the task line, as the line changes to keep ahead of the curve
What is going on?
l
Gary Marsden Slide 19University of Cape Town
Capitalism
Companies exist to make money for their share holders. This means that they need to keep selling products to the same consumers
Unlike cars (or other physical products), software (and electronics) does not ware out
Therefore, companies must make you want to buy new products - the technology curve cannot be allowed to cross the task line.
Gary Marsden Slide 20University of Cape Town
Task stepping
There are many ways to produce a stepped task curve. Here are three:– Forwards compatibility
• Having software versions which are incompatible
– Processor exploitation• Here is a quote from a Microsoft executive:
– “if we hadn’t brought your processor to its knees, why else would you get a new one.”
– Snobbery• Word processing - “font-itis”, “clipart-itis” etc.
Gary Marsden Slide 21University of Cape Town
Usability exploitation
Companies can also exploit usability to step the task line using marketing and drama– Drama
• Exploits the fact that products can be made to look easy to use at purchase time
• Sales people use “demo” buttons or careful walkthroughs
– This is backed by marketing• Microsoft head of marketing “perception is reality”• Techno-centric focus (“Super-Intelligent control”)
Gary Marsden Slide 22University of Cape Town
Complicity
Most users are happy to be exploited in this way for many reasons
Don’t want to admit they have made a bad decision
Enjoy the kudos that comes from knowing a system and helping others
• Early adopters buy for fashion purposes
Moreover, users do not know that there are better ways of doing things
• as the technology is hard to understand, users assume un-usability is essential
Gary Marsden Slide 23University of Cape Town
Increasing usability awareness
Before we start to look at how programmers improve usability, it is worth considering how usability awareness can be raised– Commercial
• new user groups and applications, esp. cellular phones• little need whilst still selling
– Academic• little impact in three decades
– Consumer groups• need to develop usability standards (I have done a lot
of work here)
Gary Marsden Slide 24University of Cape Town
Building better systems
There has been much work in HCI on principles for interface design
We shall look at a few of these and see how they can be applied to common systems
Remember these are principles for programmers - there is much more to HCI especially in prototyping, evaluation and user centred design
Gary Marsden Slide 25University of Cape Town
Affordance (Don Norman)
Affordances of an object are those properties of the object which give users clues as to how the device is used– Good examples include push buttons and levers– Bad examples:
• Pet hate is Web site design where links are not underlined and give no indication of how they should be used.
Gary Gary GaryGary
Gary
Button Graphic Traditional Rollover No affordance
Gary Marsden Slide 26University of Cape Town
Affordance examples (UCT)
Gary Marsden Slide 27University of Cape Town
Mapping (Don Norman)
Mapping is concerned with ensuring that there is a natural correlation between objects and the interface controlling them
This crops up with oven controls, light switches and, our old friend, the car radioBeware of cultural mappings as opposed to ‘real’ mappings
Gary Marsden Slide 28University of Cape Town
Constraints (Don Norman)
Constraining a design so that it can only be used the correct way– Lego– 3.5” disks– Greyed menu options
Gary Marsden Slide 29University of Cape Town
Visualising (Don Norman / Ben Shneiderman)
Features should be made visible - we talked about this earlier– Bad (usually impoverished interface)
• Command lines• Cellular phone menus
– Good• Direct Manipulation• Menu systems
Gary Marsden Slide 30University of Cape Town
Memory (Don Norman & many others)
Essentially memory comes in two flavours– Short term– Long term
Short term memory is like RAM and can hold 7±2 items at a time. This impacts issues like menu design
Long term is like hard disk. Too complicated to go into here
Also linked to cognitive models
Gary Marsden Slide 31University of Cape Town
Knowledge & Chunking (Don Norman etc.)
To improve on memory, we tend to chunk actions– Chunking works by grouping actions into a lump– Seek for meaningful relationships. Here is my UK
cellphone number written two ways:• 0976 609766• 09766 09766
To help, we need to differentiate “knowledge in head” and “knowledge in world”– Display based action– Recognition vs. recall
Gary Marsden Slide 32University of Cape Town
Conceptual Models and task analysis (Don Norman etc.)
Task analysis techniques like GOMS, which you have covered already, help programmers think about the user goals and task closure– ATM machines fail on the closure test
Conceptual models require the programmer to think about how the user is conceptualising a problem and build an accurate representation
When the user model and the computer model do not match, we have “cognitive dissonance”
Gary Marsden Slide 33University of Cape Town
Reverse Turing test (Harold Thimbleby)
Humans should be treated at least as well as computers
Explains why direct manipulation better than guided dialog (as per VCR timer recording)
Sounds obvious, but this has huge impact on interface design
We will look at this point a lot more in the case studies
Gary Marsden Slide 34University of Cape Town
Role Integrity (Harold Thimbleby)
Interfaces should not mislead users about what the computer is capable of
This usually applies to hidden limits such as– Midi sequencers coping with only eight tracks
Generally limits should be zero, one or infinity
If the interface is capable of specifying a task, the computer should be able to complete it
Gary Marsden Slide 35University of Cape Town
Simpler is not always better (Harold Thimbleby)
Einstein’s “Everything should be made as simple as possible, but not simpler”
Fewer buttons often seen as simpler, but not always the case– Overloading buttons with modes
• Typewriters are easy to use• My Navi-key Nokia is not
Complex looking buttons can be hid under a lid
Gary Marsden Slide 36University of Cape Town
Principle of least astonishment (Harold Thimbleby)
Consistency is obviously a key goal in interface design.
This has been stated as– “The principle of least astonishment”
Consistency applies to functionality and form– The car radio displays both types of inconsistency
• Button layout on face / button layout on remote control• Functionality of RDS modes
Gary Marsden Slide 37University of Cape Town
Modes (Harold Thimbleby etc.)
Modes allows different behaviours from the same interface features
Not necessarily bad, but linked to poor feedback, can be awful
• Buttons 7-12 on the radio
For users who are not aware that the mode has changed, this makes the device appear non-deterministic– Polya’s principle of “Non-sufficient reason” - if
there is no reason to believe things are different, they aren’t
Gary Marsden Slide 38University of Cape Town
Equal opportunity (Harold Thimbleby & Andy Monk)
Equal opportunity states that there should be no difference between input and output values (or known / unknown) - one can be substituted for the other.
Good examples include:– Spreadsheets - cells are neither input or output
exclusively– Camera aperture / shutter speed – Zloof Query by Example
Gary Marsden Slide 39University of Cape Town
Principle of least effort (Harold Thimbleby)
Zipf’s principle of least effort can be rewritten as:– “Make frequent things easy, unlikely things
harder”
Similar to the simplicity idea, this manifests in the following ways– Morse code ‘E’ is only one dot, apostrophe is 6
dots and dashes– Menus organised to common things at top– “Dangerous” operations could be heavily nested
or require many clicks or presses
Gary Marsden Slide 40University of Cape Town
Feedback (Harold Thimbleby & Isaac Newton)
Newton taught us that every action in nature is met with a reaction - this is not always the case in interfaces
Every user action needs the interface to react so that the user knows the action is complete– this can be tricky in multi-tasking systems
Especially important for displaying modal information
Gary Marsden Slide 41University of Cape Town
Fitts’ Law
“The time taken to acquire a target is a function of the distance to and size of the target”
For a target of size S, a distance D from the pointer, time is– a+b*log2(D/S + 1) (a and b depend on device
characteristics)
This has big implications for items such as menu design
Gary Marsden Slide 42University of Cape Town
Bruce “Tog” Tognazzini
Somewhat of a character, Tog is well known as an outspoken proponent of good interface design
Almost unique in HCI community he worked for a real company (Apple) and was responsible for designing real products (System 7 among them)
He is not a whinge-bag
Gary Marsden Slide 43University of Cape Town
Tog’s ideas
Anticipation / Autonomy– Do not try to guess what your users want– Give them some room to explore (more
than an ATM, less than UNIX)
Colour Blindness– Never use as a primary queue
Consistency– Inconsistency just as important
Defaults– Never called “Default” – easy to over-ride
Gary Marsden Slide 44University of Cape Town
Tog continued
User efficiency– Do not confuse machine with user efficiency
Latency reduction– Use threads!
Use metaphors– but not too much (what the heck is an
analogy?)
Protect your users
Gary Marsden Slide 45University of Cape Town
Genuine Usability
We are going to look at some results from a usability test on mobile phones conducted by US-West
Before we look at the results, what do you think of handset usability and how practice, age and instruction might affect it?
Interesting study as purchasers are not the end user
Gary Marsden Slide 46University of Cape Town
Usability experiment
US-West carried out a series of tests with a diversity of subjects
They had to complete 28 tasks on 3 different handsets. Times were measured and compared
Subjects were also interviewed about phone preferences
Gary Marsden Slide 47University of Cape Town
Task results
Similar usabilityPlenty of “room for improvement”Varied success
– basic features good– advanced / vertical services were awful
Practice doesn’t help muchVery poor feedback
– possibly a problem of handset and network feature confusion
Age makes a big difference
Gary Marsden Slide 48University of Cape Town
Consequences
Reduced network usage– Speed dials; 16% success– Save from call log; 25% success– many don’t try
Reduced usage of vertical servicesVulnerability to competition
Gary Marsden Slide 49University of Cape Town
Manuals & Instruction
Can help with success– Need to be tailored for age / gender etc.
• Fonts hard to read for elderly
– Poorly optimised dialog• “Call forwarding is on” Vs.• “Your feature has been activated” Vs• stutter dialtone
Instructions are age related– “Nintendo effect” cross over point
Gary Marsden Slide 50University of Cape Town
Second experiment
A second experiment was conducted to check physical attribute preference
Before looking at the next page, what do you think are the attributes people look for– size– colour– battery life
Are attributes the same for different groups of people.
Gary Marsden Slide 51University of Cape Town
Results
Long battery life is important– for men– for experienced users
Smaller and lighter are good, unless:– you are an experienced user– you are a kid
Too small is badBigger displays important
– especially to elderly
Gary Marsden Slide 52University of Cape Town
Conclusions
Manufacturers must resist “Swiss Army” phones– creeping featurisim– features as rewards like Nintendo
Touch screens seem way forward Usability must improve to reduce calls to support
line but increase calls to vertical services
Network suppliers are not happy with usability Handset manufacturers are more likely to listen to
service providers than individual customers
Gary Marsden Slide 53University of Cape Town
Using Design Rules
Attempt to provide designers with information about impact of their designs
Always a trade-off - the more general the rule, the more chance it conflicts with another rule
We can make a vague distinction between:
Guidelinesvague, need to know theoretical underpinning
Standardscan be very specific, e.g 3-button mice used
Guidelines
Standards
Authority
Generality
Gary Marsden Slide 54University of Cape Town
Standards
Usually set by international committee– Hardware standards more specific than software– Hardware less likely to change
Strength lies in forcing a large community to follow standard
Currently not much for promoting usability: tend towards ‘de facto’ standards
Gary Marsden Slide 55University of Cape Town
Guidelines
Style guides published by Apple, Sun etc.Tend to be generalisations - the more
general, the earlier they should be in the design process
Can range from:– Users must initiate all dialog (Apple)to– Use white space between long groups of menu
controls (Open Look)
Gary Marsden Slide 56University of Cape Town
Summary
Standards
High authority
Little overlap
Limited application
Minimal interpretation
Guidelines
Lower Authority
Conflicts / overlap / trade-off
Less focused
Interpretation required - HCI background
Gary Marsden Slide 57University of Cape Town
Web Guides
For the coursework, you will need to find a style guide for the site design
As there are so many styles of site, make sure you find one which suits the site you are interested in
I will give you a list of style guides, but here are some good design rules from Jakob Nielsen (Web guru)
http://www.useit.com
Gary Marsden Slide 58University of Cape Town
To 10 points of bad design
Breaking the back button Opening browser windows Non-standard use of widgets Lack of biography No archives Moving URL’s “Smart” headlines Buzzwording Slow sites Any advertising, or similar graphic
Gary Marsden Slide 59University of Cape Town
Writing for the Web
Simplicity and informality Credibility Outbound links for credibility Low humour Speed Scanable text (bullet points) Concise (half word count of other media) Summaries / Inverted pyramid Graphics and text integrated
Check Strunk and White