05-830, User Interface Software, Spring, 1999
Lecture 1,   January 11, 1998
Copyright © 1999 - Brad Myers

Why are Interfaces Important, and
Why are they Hard
To Design and Implement?

Why Are User Interfaces Important?

• Sit-down-and-use computers and software
  • don't read the manuals
• Usability is critical to software sales:
  • In magazine ratings
  • "User friendly"
• Productivity paradox
• HCI-trained people build better interfaces.
  • Programmers don't think like end-users
  • Exposure to different kinds of interfaces, problems
  • Can't "unlearn" something
  • User model, not system model
  • Guidelines
• There are well-defined methods and techniques
• Not just opinions, luck, domain-experience
• Very expensive to not do usability engineering
  • Interfaces will be re-designed: before or after release
  • Studies show that usability engineering saves money
    • $39,000 $613,000 $8,200,000
    • Up to 5000 times the cost
  • Disasters
    • Aegis
    • Therac-25
• Recognized by industry, government, etc.
  • Plenty of jobs.
  • Money for research
• Significant time and code devoted to HCI now
  • Brad A. Myers and Mary Beth Rosson. "Survey on User Interface Programming," Proceedings SIGCHI'92: Human Factors in Computing Systems.  Monterrey, CA, May 3-7, 1992. 195-202.

Percent devoted to the UI:

Why Are User Interfaces Hard to Design?

• ``It is easy to make things hard. It is hard to make things easy.''
• User Interface design is a creative process
• Designers have difficulty thinking like users
  • "Know thy user"
  • Often need to understand task domain
  • Specifications are always wrong:

    "Only slightly more than 30% of the code developed in application software development ever gets used as intended by end-users. The reason for this statistic may be a result of developers not understanding what their users need."
    -- Hugh Beyer and Karen Holtzblatt, "Contextual Design: A Customer-Centric Approach to Systems Design," ACM Interactions, Sep+Oct, 1997, iv.5, p. 62.

  • need for prototyping and iteration
  • What do you see in the picture?  After you know what is there, it is hard to remember how "not" to see it!
    
• Tasks and domains are complex
  • MacDraw 1 vs. Illustrator
  • CAD programs with 1000 commands
• Various aspects of the design must be balanced
  • Standards (style guides, related products)
  • Graphic design (artistic)
  • Technical writing (Documentation)
  • Internationalization
  • Performance
  • High-level and low-level details
  • External factors (social issues)
  • Legal issues
  • Time to program and text
  • Special requirements (CSCW, etc.)
• All UI design involves tradeoffs
• Existing theories and guidelines are not sufficient
  • Too specific and/or too general
  • Standard does not address all issues.
  • Macintosh standard UI could be all dialog boxes and menus.
  • Not sufficient just to use icons and windows
• Iterative Design is difficult
  • Getting users
  • Running tests
  • Changes make the system worse

Why Are User Interfaces Hard to Implement?

• They are hard to design, requiring iterative implementation
  • Not the waterfall model: specify, design, implement, test, deliver.
• They are reactive and are programmed from the "inside-out"
  • Event based programming
  • More difficult to modularize
• They generally require multi-processing
  • To deal with user typing; aborts
  • Window refresh
  • Window system as a different process
  • Multiple input devices
• There are real-time requirements for handling input events
  • Output 60 times a second
  • Keep up with mouse tracking
  • Video, sound, multi-media
• Need for robustness
  • No crashing, on any input
  • Helpful error messages and recover gracefully
  • Aborts
  • Undo
• Lower testability
  • No tools for regression testing
• Little language support.
  • Primitives in computer languages make bad user interfaces
  • Enormous, complex libraries
  • Features like object-oriented, constraints, multi-processing
• Complexity of the tools
  • Six books for Macintosh Toolbox
• Difficulty of Modularization

Example: Reading a filename

Strategy	Problem
1) Readln() in Pascal.	if wrong, aborts
2) Loop reading name	no ability to look for file
3) add window system	can look, but need to retype (requires multi-processing, window refresh, etc.)
4) add cut/paste	user needs to know how to run ls
5) add menu of file names	need to be able to change directories
6) add that	want to create directories, also
7) add that	want to be able to abort reading a file (requires that read have an error return)
8) add that	want context-dependent help system (e.g., to describe why file is wanted and how to get it)
9) add that	want UNDO (mostly useful for writing; implies backup copies)
10) and on and on ....

• Now have lots of software just to read a filename!

HCI At CMU:

• Human-Computer Interaction Institute
  • Over 50 professors associated with it
  • MS and BS programs
  • Discussions of PhD programs
  • http://www.cs.cmu.edu/~hcii
• Weekly HCI seminar series
  • Wednesday afternoons at 3:30 in 5409
• Formerly had monthly "CHI Klatch" lunches for graduate students and faculty
  • Suspended for lack of interest
• (Separate) monthly lunches for faculty
• Let me know if you want to be on the HCII mailing list

Exercise:

• Think of some problems with the standard user interface of the Macintosh and Windows95 systems.
  • Especially in the fundamental interaction techniques common to both
• Propose solutions to these problems
• What are the problems with your solutions?
• Some problems I came up with...

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