CS 501: Software Engineering

1. CS 501: Software Engineering Lectures 11 & 12 Usability

2. Course Administration Quiz 2 on Thursday Same format as the first quiz Quiz 3 will be on March 16

3. Presentations Project Presentations First presentation is next week, Tuesday through Thursday. Meeting room is at 301 College Avenue. For instructions, read the Assignments page. Schedule your presentation now!!!! Available time slots are on the Home page. Your client must attend the presentation unless you have special permission.

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

5. Software Design The design phase is the most creative part of software development. 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)

6. Lectures on Design Lectures Topic 11-12 Usability 13-14 System Architecture 15-18 Object Oriented Design

7. Usability: Reading Reading:  Mitchell Kapor, A Software Design Manifesto. Dr. Dobbs Journal, 1991. http://hci.stanford.edu/bds/1-kapor.html "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."

8. Usability: The Design/Evaluate Loop Design Analyze requirements ? Build Evaluate

9. 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?

10. Design from a System Viewpoint interface design functional design data and metadata computer systems and networks mental model

11. Mental Model The mental (conceptual) model is the user's internal model of what the system provides: • The desk top metaphor -- files and folders • The Web model -- pages with hyperlinks

12. What a person thinks is true about a system, not necessarily what is actually true Similar in structure to the system that is represented Allows a person to predict the results of his actions Simpler than the represented system. A mental model includes only enough information to allow accurate predictions (i.e. no data structures) Also called conceptual model Mental Model

13. Interface Design The interface design is the appearance on the screen and the actual manipulation by the user • Fonts, colors, logos, key board controls, menus, buttons • Mouse control or keyboard control? • Conventions (e.g., "back", "help") Examples: • Screen space utilization in Acrobat. • Number of snippets per page in Web search.

14. 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 should be offered shortcuts; beginners should have simple, well-defined options The user should feel in control

15. Functional Design The functional design, determines the functions that are offered to the user • Selection of parts of an object • Searching a list or sorting the results • Help information • Manipulation of objects on a screen • Pan or zoom There may be many user interface choices for the same function, e.g., Macintosh v. Windows desktop

16. Data and metadata Structural data and metadata stored by the computer system enable the functions and the interface • Effectiveness of searching depends on the type and quality of data that is indexed (free-text, controlled vocabulary, etc.) • The desktop metaphor has the concept of associating a file with an application. This requires a file type to be stored with each file: -- extension to filename (Windows and Unix) -- resource fork (Macintosh)

17. Computer systems and networks The performance, reliability and predictability of computer systems and networks is crucial to usability

18. Non-functional Requirements Performance, Reliability, Scalability, Security… Example: Response time0.1 sec – the user feels that the system is reacting instantaneously1 sec – the user will notice the delay, but his/her flow of thought stays uninterrupted10 sec – the limit for keeping the user's attention focused on the dialogue

19. 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

20. 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

21. 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

22. 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 choices • Scrolling menus (e.g., states of USA) • Hierarchical • Associated control panels • Menus plus command line Users prefer broad and shallow to deep menu systems

23. 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! *

24. Information Presentation Simple is often better than fancy • Text precise, unambiguous fast to compute and transmit • Graphical interface simple to comprehend / learn uses of color shows variations

25. Information Presentation: Separation of Presentation from Content Acrobat Presentation software PDF Display Information to be displayed html Presentation software Display Firefox

26. System Considerations of User Interfaces • Personal computer cycles are there to be used • Any network transfer involves delay • Shared systems have unpredictable performance • Data validation often requires access to shared data • Mobile code poses security risks

27. The process of determining the worth of, or assigning a value to, the usability on the basis of careful examination and judgment. Making sure that a system is usable before launching it. Iterative improvements after launch. Categories of evaluation methods: Analytical evaluation: without users Empirical evaluation: with users Measurements of operational systems Evaluation

28. How do you measure usability? Usability comprises the following aspects: Effectiveness – the accuracy and completeness with which users achieve certain goals Measures: quality of solution, error rates Efficiency – the relation between the effectiveness and the resources expended in achieving themMeasures: task completion time, learning time, clicks number Satisfaction – the users’ comfort with and positive attitudes towards the use of the systemMeasures: attitude rating scales From ISO 9241-11 Evaluation

29. Assessing systems using established theories and methods Evaluation techniques Heuristic Evaluation (Nielsen, 1994) Evaluate the design using “rules of the thumb” Cognitive Walkthrough (Wharton et al, 1994) A formalized way of imagining people’s thoughts and actions when they use the interface for the first time Claims Analysis – based on scenario-based analysis Generating positive and negative claims about the effects of features on the user Evaluation without Users

30. 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.

31. Analysis of system logs • Which user interface options were used? • When was was the help system used? • What errors occurred and how often? • Which hyperlinks were followed (click through data)? Human feedback • Complaints and praise • Bug reports • Requests made to customer service Evaluation based on Measurements

32. Testing the system, not the users! Stages of evaluation with users: Preparation Sessions conduct Analysis of results Evaluation with Users User testing is time-consuming and expensive.

33. Determine goals of the usability testing “The user can find the required information in no more than 2 minutes” Write the user tasks “Answer the question: how hot is the sun?” Recruit participants Use the descriptions of users from the requirements phase to detect potential users Evaluation with UsersPreparation

34. Usability Laboratory Concept: monitor users while they use system Evaluators User one-way mirror

35. Conduct the session Usability Lab Simulated working environment Observe the user Human observer(s) Video camera Audio recording Inquire satisfaction data Evaluation with UsersSessions Conduct

36. If possible, use statistical summaries Pay close attention to areas where users were frustrated took a long time couldn't complete tasks Respect the data and users' responses, don't make excuses for designs that failed Note designs that worked and make sure they're incorporated in the final product Evaluation with UsersResults Analysis

37. Evaluation Example: Eye Tracking

38. Evaluation Example: Eye Tracking

39. Refining the design based on evaluation Designers and evaluators need to work as a team Designers are poor evaluators of their own work, but know the requirements, constraints, and context of the design: • Some user problems can be addressed with small changes • Some user problems require major changes • Some user requests (e.g., lots of options) are incompatible with other requests (e.g., simplicity) Do not allow evaluators to become designers

40. The Importance of User Interface Design Good support for users is more than a cosmetic flourish • Elegant design, appropriate functionality, & responsive system: => a measurable difference to their effectiveness • A system that is hard to use: => users may fail to find important results, or mis-interpret what they do find => user may give up in disgust A computer system is only as good as the interface it provides to its users

41. User Interface Design Examples of change: 1990 to 2006

42. 1990

43. 1995

44. 2003

45. 2003

46. 1995

47. 2006

48. 1995

49. 2003

50. 1995