1. 2. Guidelines, Principles and Theories

2. Guidelines: Low-level focused advice about good practices and cautions against dangers.
Principles: Mid-level strategies or rules to analyze and compare design alternatives.
Theories: High-level widely applicable frameworks to draw on during design and evaluation, as well as to support communication and teaching.

3. A Rule externally compels you, through force, threat or punishment, to do the things someone else has deemed good or right. People follow or break rules.
A principle internally motivates you to do the things that seem good and right. People develop principles by living with people with principles and seeing the real benefits of such a life.
A guideline is the information intended to advise people on how something should be done
Theories - A set of statements or principles devised to explain a group of facts or phenomena, a statement or procedure by which to determine a course of action
Eg: guidelines for the completion of tax returns.

4. Guidelines
Narrowly focused
promote consistency among multiple designers in terminology usage, appearance, and action sequences
Critics
Too specific, incomplete, hard to apply, and sometimes wrong

5. 1. Navigating the interface
Difficult for many users- rules will be helpful (+ve / -ve)
National Cancer Institute’s guidelines
Standardize task sequences- users perform tasks in same sequence & manner across similar conditions
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

6. 2. Organizing the display
Smith and Mosier (1986) offer five high-level goals – data display
Consistency of data display
color, format, abbreviation, capitalization, similar delimiters
2) Efficient information assimilation by the user
format –familiar, related to the task
Rules- left justification for alphanumeric data, right justification of integers,
proper spacing

7. 3) Minimal memory load on the user
Minimal steps to complete the task
4) Compatibility of data display with data entry
5) Flexibility for user control of data display
Order of columns, sorting of rows – must be changeable by users

8. 3. Getting the user’s attention
Intensity – popups small window
Marking – underline, box, arrow, *, +, X
Size – up to 4 levels
Choice of fonts – up to 3 fonts
Inverse video – inverse coloring
Blinking – blinking color display
Color – up to 4 colors
Audio – soft tone, hard tone

9. 4. Facilitate data entry
Data entry- time consuming, frustrating, dangerous errors
Consistency of data entry transactions
Minimal input actions by user
menu, single keystroke / typing, redundancy must be avoided
3) Minimal memory load on the user – lengthy list of codes
4) Compatibility of data entry with data display
5) Flexibility for user control of data entry
Air traffic control environment

10. Principles
more fundamental, widely applicable, Need more clarification
Determine user’s skill levels
Learning about the users – simple & difficult
Never ending – users keep changing
User age, gender, education, culture, personality etc
Some users may prefer – tables, graphs, words
Novice/first time users
Knowledgeable intermittent users
Expert frequent users

11. 3. Choose an interaction style
2. Identify the tasks
After knowing users, developers must identify the tasks to be carried out
Decomposition of high level tasks
Example: Word Processor
Frequent actions - arrow keys, insert, delete
Less Frequent actions –single letter plus Ctrl key
3. Choose an interaction style
Direct manipulation
Menu selection
Form fill-in
Command language
Natural language

13. 4. The 8 Golden Rules of Interface Design
Strive for consistency – color, layout, capitalization, font
Cater to universal usability
Offer informative feedback- for every user action
Design dialogs to yield closure- actions must be organized into groups
Prevent errors – design should be such that users don’t do serious errors
Permit easy reversal of actions- relieves anxiety, explore unfamiliar options
Keep users in control – users don’t want surprises and changes
Reduce short-term memory load – avoid interfaces in which users need to remember data

14. 5. Prevent errors
A way to reduce loss in productivity due to errors – improve error messages - specific, positive in tone, and constructive
Correct actions
Gray out inappropriate actions
Selection rather than freestyle typing – date from calendar
Automatic command completion – visual basic-fewletters
Complete sequences
Single switch – turn on signal lights on L/R of the car
Single command – to change style of all the titles

15. 6. Automation and human control
Reduces the potential for errors & user’s workload
An automate system
Pilot 1 – request clearance for an emergency landing- failed engine
Pilot 2 – reports a passenger with chest pain
In such cases need human judgement to decide which plane should land first
Air traffic control
Design must “Improve system performance, without reducing human involvement”

16. Theories
Principles are used to develop theories
Some theories are
Descriptive - description of the behavior, event, or object
Explanatory -why and how a thing works , explanation of why a phenomenon is the way it is
Prescriptive – gives directions or rules as to how something should work or be carried out.
Predictive – compare designs wrt execution time, error rates , predict outcomes based on the changing values of component variables.

17. To Guide practice (Prescriptive)
To explain phenomena (Explanatory)
To predict outcome (Predictive)
To Enlighten understanding (Descriptive)

18. Taxonomy (explanatory theory)
Order on a complex set of phenomena
Facilitate useful comparisons
Organize a topic for newcomers
Guide designers
Indicate opportunities for novel products

19. Design by levels
Conceptual level:
identifies the set of familiar task-oriented objects and actions the user needs to know about in order to use the system
Semantic level:
describes the meanings conveyed by the user's command input and by the computer's output display - delete object/undo

20. Syntactic level:
identifies the sequence of inputs and output
Lexical level:
deals with device dependencies and with the precise mechanisms by which a user specifies the syntax - function key/ mouse double click

21. Conceptual: Provides a mental model
Example: text editor objects = characters, files, paragraphs relationships = files contain paragraphs contain chars operations = insert, delete, etc.
Semantic: meaning/desired function
Example: move the paragraph
Syntactic: how the semantic command is formed
Example: prefix vs. postfix (Edit, Highlight, Cut, Paste)
Lexical: sequence of actions
Example: how mouse and keyboard combined into menu, button, string, pick, etc. Point to edit on menu bar->click ->select option within edit menu.

22. 2. Stages of action models
Norman's seven stages of action – explanatory model of HCI
Forming the goal
Forming the intention
Specifying the action
Executing the action
Perceiving the system state
Interpreting the system state
Evaluating the outcome

23. Norman's seven stages of action

24. Example

26. 3. Consistency
An important goal for a designer is a consistent UI
Consistent use of color, layout, icons, font, button sizes - gives user a clear understanding of the interface
Inconsistent action -Take longer to learn, cause more errors, slow down users, and are harder for users to remember
Design of mobile devices
Initiating actions – left side buttons
Terminating actions – right side buttons
Up-down actions using vertically & horizontally aligned button

27. The End