1. CS 501: Software Engineering
Lecture 11
Usability 1

2. Presentations Project Presentations
First presentation is next week, Wednesday through Friday (note change of date)
For instructions, read the Assignments page.
Schedule your presentation now!!!!
Available time slots are on the Notices page.
Your client must attend the presentation unless you have special permission.

3. Planning for the Presentation
How will you use the time?
This is a presentation to the client, with the Instructor as a
secondary audience. Possible topics:
• Overview of project and progress against plan
• Presentation of assumptions, decisions
• Summary of requirements in moderate detail
• What has been learned since feasibility study. Changes in plans
Allow 15 minutes for questions. Expect interruptions.
"This is our understanding of your requirements."

4. Planning for the Presentation
Logistics
Have a rehearsal, check visual aids and demonstrations. Then change nothing.
Check out the equipment in the meeting room. What network will you use (if any). How will you connect a computer (if you do)? What about firewalls?
Will one person act as chair and call on other members of the team? Never interrupt your colleagues.
Not everybody is a great presenter, but everybody can be
well-prepared.

5. Design Your understand the requirements, now to design the system.
Feasibility and
Planning
Requirements
Design
Operation and
Maintenance
Implementation

6. What is Design? Design is conscious
Design keeps human concerns in the center
Design is a dialog with materials
Design is creative
Design is communication
Design has social consequences
Design is a social activity
Terry Winograd
Bringing Design to Software, 1996

7. Software Design The design must: • Meet the requirements
• Satisfy the users
• Provide flexibility for changing requirements
• Be suitable for implementation with available resources
• Be testable and maintainable
• Fit within the style of the organization(s)

8. Reading
Required Reading:  Mitchell Kapor, A Software Design Manifesto. Dr. Dobbs Journal,
"Software design is not the same as user interface design."
"Architects, not construction engineers, are the professionals who have overall responsibility for creating buildings. ... in the actual process of designing and implementing the building, the engineers take direction from the architects."

9. Lectures on Design Lectures Topic 11-12 Usability
13-14 System Architecture
15-16 Object Oriented Design
17-18 Tools and Techniques

10. Design for Usability
Usability of a computer system is a combination of factors:
• User interface design
• Functionality
• Performance
• Help systems and documentation
• Freedom from errors
Anything else?

11. User Interface Design
The user interface design is the appearance on the screen and the actual manipulation by the user (look and feel)
• Fonts, colors, logos, key board controls, menus, buttons
• Mouse control or keyboard control?
• Conventions (e.g., "back", "help")

12. Same Functions, Different Interface
The user interface design is different from the functionality provided.
Example 1: Microsoft Word on Windows and Macintosh:
• Different user interfaces for the same functionality.
Example 2: The desk top metaphor
• Mouse -- 1 button (Macintosh), 2 button (Windows) or 3 button (Unix)
• Close button -- left of window (Macintosh) right of window (Windows)

13. User Interface Design
Examples of change: 1990 to 2003

14. 1990

15. 1995

16. 2003

17. 1995

18. 2003

19. 1995

20. 2003

21. 1995

22. 2003

23. User Interface Design: Requirements and Refinement
It is very difficult to specify and comprehend an interactive
interface in a textual documents.
Requirement documents benefit from sketches, comparison with existing systems, etc.
Design documents should definitely include graphical elements and often benefit from a mock-up or other form of prototype.
Implementation plans should include evaluation of user factors and time to make changes.

24. The Design/Evaluate Loop
Analyze requirements ?
Build
Evaluate

25. Mock-up Example

26. Methods for Specifying Usability Requirements and Evaluation of Usability
Initial Mock-up Prototype Production
Client's opinions   
Competitive analysis 
Expert opinion  
Focus groups  
Observing users   
Measurements  

27. Focus Group A focus group is a group interview • Interviewer
• Potential users
Typically 5 to 12
Similar characteristics (e.g., same viewpoint)
• Structured set of questions
May show mock-ups
Group discussions
• Repeated with contrasting user groups

28. Usability Laboratory
Monitor users while they use system (or a prototype)
Evaluators User
one-way mirror

29. Usability Laboratory

30. Usability Laboratory Observing techniques • Human observer
• Video camera
• Tape recording
Study techniques
• Human protocol (user talks aloud while using system)
• User carries out specified list of tasks
• Software designer presents story board (mock-up) to user

31. Eye Tracking

32. Eye Tracking

33. Measurement
Basic concept: log events in the users' interactions with a system
Examples from a Web system
• Clicks (when, where on screen, etc.)
• Navigation (from page to page)
• Keystrokes (e.g., input typed on keyboard)
• Use of help system
• Errors
May be used for statistical analysis or for detailed
tracking of individual user.

34. Principles of Interface Design
Interface design is partly an art; there are general principles:
• Consistency -- in appearance, controls, and function.
• Feedback -- what is the computer system is doing? why does the user see certain results?
• Users should be able to interrupt or reverse actions
• Error handling should be simple and easy to comprehend
• Skilled users offered shortcuts;
beginners have simple, well-defined options
The user should feel in control

35. Style of User Interfaces: Command Line Interfaces
User interacts with computer by typing commands
• Allows complex instructions to be given to computer
• Facilitates formal methods of specification & implementation
• Skilled users can input commands quickly
• Requires learning or training
• Can be adapted for people with disabilities
• Can be multi-lingual
• Suitable for scripting / non-human clients

36. Style of User Interfaces: Direct Interaction
User interacts with computer by manipulating objects on screen
• Can be intuitive and easy to learn
• Users get immediate feedback
• Not suitable for some complex interactions
• Does not require typing skills
• Straightforward for casual users, slow for skilled users
• Icons can be language-independent
• Difficult to build scripts
• Only suitable for human users

37. Design for Direct Manipulation
metaphors and mental models: Conceptual models, metaphors, icons, but there may not be an intuitive model
navigation rules: How to move among data functions, activities and roles in a large space
conventions: Familiar aspects that do not need extra training.
=> scroll bars, buttons, help systems, sliders
=> good for users, good for designers
look: characteristics of the appearance that convey information
feel: interaction techniques that provide an appealing experience

38. Design for Direct Manipulation: Menus
• Easy for users to learn and use
• Certain categories of error are avoided
• Enables context-sensitive help
Major difficulty is structure of large menus
• Scrolling menus (e.g., states of USA)
• Hierarchical
• Associated control panels
• Menus plus command line
Users prefer broad and shallow to deep menu systems

40. Help System Design Help system design is difficult!
• Must prototype with mixed users
• Categories of help:
=> Overview and general information
=> Specific or context information
=> Tutorials (general)
=> Cook books and wizards
=> Emergency ("I am in trouble ...")
• Must have many routes to same information
Never blame the user!