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Design Principles & Platform Constraints
Transcript of Design Principles & Platform Constraints
General Design Principles
What they are:
Broad design principles designed to avoid common design pitfalls. They are derived from common design problems across many systems
What they are NOT:
Rules written in stone which must be obeyed!
a few guidelines identify many common usability problems
easily remembered, easily applied with modest effort
discount usability engineering
end users not required
cheap and fast way to inspect a system
can be done by usability experts, double experts, and end users
single evaluator only catches ~35% of usability problems
5 evaluators catch 75%
Some Sample Design Principles
Simple and natural dialogue
Speak the users’ language
Minimize user’s memory load
Provide clearly marked exits
Deal with errors in a positive manner
Research has shown that
Can’t be treated as a simple checklist.
There are subtleties involved in their use.
Due to the wide range of possible activities some of these will not be relevant to your project.
1. Simple and natural dialogue
Use the user’s conceptual model
Match the users’ task sequence Minimise mapping between
interface and task semantics
Present exactly the information the user needs
less is more
less to learn, to get wrong, to distract...
information should appear in natural order
related information is graphically clustered
order of accessing information matches user’s expectations
remove or hide irrelevant or rarely needed information
use windows frugally
2. Speak the users’ language
Terminology based on users’ language for task
Only use acronyms if you are sure the user will understand them.
3 Minimize user’s memory load
Computers good at remembering, people are not!Promote recognition over recallmenus, icons, choice dialog boxes vs commands, field formatsrelies on visibility of objects to the user (but less is more!)
4: Be consistent
Consistent syntax of inputConsist language and graphics
Same visual appearance across the system (e.g. widgets)Same information/controls in same location on all windows
Consist effects: commands, actions have same effect in equivalent situations predictability.
5: Provide feedback
Continuously inform the user about What it is doingHow it is interpreting the user’s inputUser should always be aware of what is going on
Response timehow users perceive delays <0.1s perceived as “instantaneous” 1s user’s flow of thought stays uninterrupted, but delay noticed 10s limit for keeping user’s attention focused on the dialog> 10s user will want to perform other tasks while waiting
6. Provide clearly marked exits
Users don’t like to feel trapped by the computer!should offer an easy way out of as many situations as possible
Strategies:Cancel button (for dialogs waiting for user input)Universal Undo (can get back to previous state)Interrupt (especially for lengthy operations)Quit (for leaving the program at any time) Defaults (for restoring a property sheet)
7. Provide shortcuts
Experienced users - perform frequent operations quickly
keyboard and mouse accelerators
double clicking vs menu selection
8: Deal with errors in a positive manner
& provide help
People will make errors!
Errors we makeMistakesConscious deliberations lead to an error instead of correct solution
SlipsUnconscious behaviour gets misdirected en route to satisfying goale.g. drive to store, end up in the officeshows up frequently in skilled behaviourusually due to inattentionoften arises from similar actions
Warn people that an unusual situation is occurringwhen overused, becomes an irritant
Go to the Reddit subsites called crappydesign and spoftwaregore
Find examples of the previous issues.
Different platforms have different constraints
Mobile and Apps
Mobile devices, the challenges related to performance issues are quite a bit bigger,
Limited in functionality
Limited in their resources (processing power and memory)
Connectivity that may be substantially slower or intermittent.
List and describe the platform constraints you see with your assignment.
The purpose of this step is to define the user interface‐related capabilities and constraints of the hardware and software platform for the application.
Overview: The hardware and software platform places a whole set of constraints on user interface design options.
As hardware evolves, new user interface capabilities may be introduced, such as better response times and greater modem speed and bandwidth.
Identify all relevant aspects of all hardware and
Review any platform documentation:
Interview technical staff:
Document Platform Capabilities and Constraints:
limiting factor: something that limits freedom of action
Can you think of some new hardware or software that have introduced new capabilities recently?
What are the advantages of a mobile platform?