1. Chapter 12 User Interface Design

2. Interface Design
Easy to use?
Easy to understand?
Easy to learn?

3. Interface Design Typical Design Errors lack of consistency
too much memorization
no guidance / help
no context sensitivity
poor response
arcane/unfriendly

4. Golden Rules Place the user in control Reduce the user’s memory load
Make the interface consistent

5. Place the User in Control
Define interaction modes in a way that does not force a user into unnecessary or undesired actions, e.g., spell checking
Provide for flexible interaction, e.g., keyboard, mouse, voice, etc.
Allow user interaction to be interruptible and undoable.
Streamline interaction as skill levels advance and allow the interaction to be customized.
Hide technical internals from the casual user.
Design for direct interaction with objects that appear on the screen, e.g., WYSWSG

6. Reduce the User’s Memory Load
Reduce demand on short-term memory, e.g., visual cues
Establish meaningful defaults.
Define shortcuts that are intuitive, e.g., Alt+P for print function
The visual layout of the interface should be based on a real world metaphor, e.g., bill paying system
Disclose information in a progressive fashion, i.e., organized hierarchically, e.g., underlining functions under a text style menu

7. Make the Interface Consistent
Allow the user to put the current task into a meaningful context.
provide indicator, e.g., window title, graphical icons
Maintain consistency across a family of applications.
If past interactive models have created user expectations, do not make changes unless there is a compelling reason to do so,
e.g., Alt+S for saving a file

8. User Interface Design Models
Four different models come into play
User model — a profile of all end users of the system (by human engineers)
Design model — a design realization of the user model (by software engineers)
Mental model (system perception) — the user’s mental image of what the interface is in user’s mind (by end users)
Implementation model — the interface “look and feel” coupled with supporting information (books, manuals, videotapes, etc) that describe interface syntax and semantics (by implementers)
The role of interface designer is to reconcile these differences and derive a consistent representation

9. User Interface Design Process
Four steps:
Interface analysis
Interface design
Interface construction
Interface validation
Can be represented using a spiral model, usually incorporating with prototyping

10. Interface Analysis Interface analysis means understanding
User analysis: understand the people (end-users) who will interact with the system through the interface; identity user categories
Novices
Knowledgeable, intermittent users
Knowledgeable, frequent users
Task analysis: understand the tasks that end-users must perform to do their work,
Content analysis: understand the content to be displayed in the interface
Environment analysis: understand the environment in which these tasks will be conducted.
where, user’s gesture, constraints, etc.

11. Interface Analysis -- User Analysis
Understand the users and learn what they wants
User interviews
Sales input
Market input
Support input

12. Set of Questions for User Analysis
Are users trained professionals, technician, clerical, or manufacturing workers?
What level of formal education does the average user have?
Are the users capable of learning from written materials or have they expressed a desire for classroom training?
Are users expert typists or keyboard phobic?
What is the age range of the user community?
Will the users be represented predominately by one gender?
How are users compensated for the work they perform?
Do users work normal office hours or do they work until the job is done?
Is the software to be an integral part of the work users do or will it be used only occasionally?
What is the primary spoken language among users?
What are the consequences if a user makes a mistake using the system?
Are users experts in the subject matter that is addressed by the system?
Do users want to know about the technology the sits behind the interface?

13. Interface Analysis -- Task Analysis and Modeling
Goal: Answers the following questions …
What work will the user perform in specific circumstances?
What tasks and subtasks will be performed as the user does the work?
What specific problem domain objects will the user manipulate as work is performed?
What is the sequence of work tasks—the workflow?
What is the hierarchy of tasks?

14. Interface Analysis -- Task Analysis and Modeling (cont.)
Analysis techniques
Use-cases define basic interaction
Ex. Computer-aided design system for interior design (see p. 367)
Task elaboration refines interactive tasks
Ex. Furniture layout, fabric and material selection, wall and window covering selection, presentation, costing, and shopping
Object elaboration identifies interface objects (classes)
Ex. Furniture class
Workflow analysis defines how a work process is completed when several people (and roles) are involved
Ex. Swimlane diagram for prescription refilling
Three categories of users: patient, pharmacists, physicians

15. Swimlane Diagram

16. Interface Analysis -- Analysis of Display Content
Are different types of data assigned to consistent geographic locations on the screen (e.g., photos always appear in the upper right hand corner)?
Can the user customize the screen location for content?
Is proper on-screen identification assigned to all content?
If a large report is to be presented, how should it be partitioned for ease of understanding?
Will mechanisms be available for moving directly to summary information for large collections of data.
Will graphical output be scaled to fit within the bounds of the display device that is used?
How will color to be used to enhance understanding?
How will error messages and warning be presented to the user?

17. Interface Design Steps
Using information developed during interface analysis (Section 12.3), define interface objects and actions (operations).
Written use-cases
Identify nouns (objects) and verbs (actions)
Define events (user actions) that will cause the state of the user interface to change. Model this behavior.
Depict each interface state as it will actually look to the end-user.
Indicate how the user interprets the state of the system from information provided through the interface.

18. Interface Design Steps--Example
SafeHome system use-case
I want to gain access to my SafeHome system from any remote location via the internet. Using browser software operating on my notebook computer (while I’m at work or traveling), I can determine the status of the alarm system; arm or disarm the system; reconfigure security zones; and view different rooms within the house via preinstalled video cameras.
To access SafeHome from a remote location, I provide an identifier and a password. These define levels of access (e.g., all users may not be able to reconfigure the system) and provide security. Once validated, I can check the status of the system and change status by arming or disarming SafeHome. I can reconfigure the system by displaying a floor plan of the house, viewing each of the security sensors, displaying each currently configured zone, and modifying zones as required. I can view the interior of the house via strategically placed video cameras. I can pan and room each camera to provide different views of the interior.

19. Interface Design Steps—Example (cont.)
Identify objects and actions
Access the SafeHome system
Enters an ID and password to allow remote access
Checks system status
Arms or disarms SafeHome system
Displays floor plan and sensor locations
Displays zones on floor plan
Changes zones on floor plan
Displays video camera locations on floor plan
Selects video camera for viewing
Views video images
Pans or zooms the video camera

20. Interface Design Steps—Example (cont.)

21. Interface Design Patterns
Patterns are available for
The complete UI
Page layout
Forms and input
Tables
Direct data manipulation
Navigation
Searching
Page elements
e-Commerce

22. Design Issues Response time Help facilities Error handling
length and variability
Help facilities
Error handling
No one likes bad news. Be constructive!
Menu and command labeling
Application accessibility
Internationalization

23. Design Evaluation Cycle