05-830, User Interface Software, Spring, 2001
Lecture 2,   January 17, 2001
Copyright © 2001 - Brad Myers

User Interface Styles;
Dimensions of User Interface Variability;
Benchmarking User Interfaces

Input Devices

• QUERTY keyboard (other types)
• Mouse (1, 2 or 3 buttons)
• Other pointing devices:
  • Pens or pucks on tablets
  • "Light pens" on screens
  • DataGloves, eye tracking, etc.
  • "Bat"  3-D input device
• Speech input
• Computer-connected camera
  • presence
  • free-space gestures
  • eye-tracking

Output Devices

• Older:
  • TTY on paper
  • 24x80 terminals: "glass-TTY"
  • Vector screens
• Raster-scan screens
  • Color, monochrome
• LCD panels
• Tiny, Room-size, portables, "normal size"
• 3-D devices
  • Head-mounted displays
  • Stereo
  • "Real" 3-D
• Speech output
• Non-speech audio

Examples of different types of applications

• word processors
• drawing programs, etc.
  • CAD/CAM
• hierarchy displays, like file browsers
• mail readers
• spreadsheets
• hypertext document reading
  • World-Wide-Web browsing
  • Form-based entry
• automated-teller machines (ATM)
• Virtual Reality
• Multi-media
  • Video
  • Animation
• Interactive, "real-time" games
• Controlling machinery

Metaphors

• Content metaphors
  • desktop
  • paper document
  • notebook with tabs
  • score sheet , stage with actors (Director)
  • accounting ledger (spreadsheet)
  • stereo (for all media players)
  • phone keypad
  • calculator
  • Web: "Shopping Carts"
  • Quicken: "CheckBook"
• Interaction metaphors = tools, agents: "electronic secretary"

User Interface Styles

• A method for getting information from the user or interfacing with a user.
• Some styles:
  

1. Question and answer,
2. Single character commands and/or function keys,
3. Command Language,
4. Menus
5. Forms/Dialogue Boxes
6. Direct Manipulation
7. WYSIWYG
   -- really is a subclass of DM, not another style
8. Gestures
9. Natural Language
   

• Usually, interfaces provide more than one style:
  • Command language for experts with menus for novices
  • Menus plus single characters (Macintosh & Windows)
• Appropriate style depends on type of user and task.
• Important issues:
  • Who has control?
  • Ease of use for novices.
  • Learning time to become proficient
  • Speed of use (efficiency) once become proficient.
  • Generality/Flexibility/Power (how much of user interface with this technique cover?)
  • Ability to show defaults, current values, etc.
  • Skill requirements required (e.g., typing)

1) Question and Answer:

• Computer asks questions, user answers.
• Used by some simple programs, and also expert systems.
• "Wizards" in Microsoft products
• Telephone interfaces ("press 1 for sales, 2 for support, ...")
• Pros and cons:

  + Easy to implement (writeln, readln)

  + Easy for novices

  - Can't correct previous errors, or to change your mind.

  • Except in Wizards, often have a "Previous" button

  - Can be slower for experts

2) Single character commands and/or function keys:

• Function keys can be labeled.
• Pros and cons:

  + Fastest method for experts.

  + Easy to learn how.

  + so easier to provide telephone support ("just hit the F1 key now")

  + Usually very simple to implement.

  - Hardest to remember which key does what.

  - Easy to hit wrong key by mistake

3) Command Language:

• User types instructions to computer in a formal language.
• Pros and cons:

  + Most flexible.

  + Supports user initiative.

  + Fast for experts.

  + Possible to provide programming language capabilities for macros, customization, etc.

  + Takes less space on screen

  - Hardest for novices.

  - Requires substantial training and memorization.

  - Error rates usually high.

  - Syntax is usually very strict.

  - Poor error handling.

  - Hard for user to tell what can do.

• Implementation difficulty depends on availability of tools like LEX & YACC, and the complexity of the language.
• Related form is programming language extensions, such as in Lisp.

4) Menus:

• Pros and cons:

  + Very little training needed

  + Shows available options

  + Allows use of recognition memory (easier than generation)

  + Hierarchy can expand selection

  + Default or current selection can be shown.

  + Ability to show when parts are not relevant (e.g., greyed out)

  + Can be used for commands and arguments

  + Reduces keystrokes (compared to command languages)

  + Clear structure to decision making.

  - Usable only if there are few choices

  - Slow for experienced users (need accelerators)

  - If big hierarchy, commands can be hard to find

  - Uses screen space

• Most effective with pointing device.

5) Form Filling

• Like menus except have text/number fields that can be filled in.
• Often used on character terminals (e.g., for data entry).
• Macintosh and Windows Dialog Boxes are another example.
• Pros and cons: (Similar to menus)

  + Simplifies data entry.

  + Very little training needed

  + Shows available options

  + Allows use of recognition memory (easier than generation)

  + Ability to show defaults and current values.

  + Ability to show when parts are not relevant (e.g., greyed out)

  - Consumes screen space.

  - Expensive to internationalize.

• Most effective with pointing device.
• Apparently, most user interfaces are of this form
• Specialty of Visual Basic

6) Direct Manipulation

• Definition:
  • Visual Model of the world
  • Visual objects that can be operated on
  • Results of actions are reflected in the objects immediately.
  • Objects, once operated on, can be further operated on.
• Term coined by Ben Shneiderman
• Original system: Sketchpad from 1962
• "Object-oriented" from user's point of view
  • As opposed to "function-oriented"
  • Usually select object, then give command
  • Hollan argues this user feel more important to DM than Shneiderman's methods
• Pros and cons:

  + User initiated

  + Easy to learn, intuitive, analogical

  + Fast to use for object that are on the display

  + Easily augmented with menus and forms

  + Provides closure of actions and gesture.

  + Errors can be avoided.

  + High subjective satisfaction (fun).

  - Can be inconvenient and slow if user knows the name of an undisplayed object, but must find it anyway.

  - Limited power; not all desired actions have a DM analog.

  - Difficult to provide macros, other user extensible/customizable features.

  - Difficult to implement.

7) WYSIWYG:

• "What you see is what you get".
• Like direct manipulation, but more so.
• Pros and cons: (Similar to direct manipulation)

  + Can always tell what final result will be.

  - Screen image may be hard to read/interpret, especially if screen resolution is too low.

  - Cannot show hidden structure (how the picture was made).

  - May be very slow at run-time (e.g., page breaks)

  - Extremely difficult to implement.

  - WYSIATI: What You See Is All There Is - lack of structure; no ability to show structure

• "Natural" actions invoke computer response.
• 8) Gestures and 9) speech
• Issues: mis-interpretation, feedback

8) Gestures:

• Like user would mark on paper.
• Pros and cons:

  + Can be very natural to learn.

  + Often faster to execute than other techniques.

  + Give command and parameters together

  - Many gestures are hard to do with a mouse.

  - Users must memorize gestures.

  • No "affordances"

9) Natural Language

• E.g., a subset of normal English.
• Includes speech
• Pros and cons:

  + Theoretically easiest for learning.

  + Speaking is the fastest output technique.

  - Rather slow for typing

  - Requires clarification dialog.

  - Unpredictable.

  - General systems are impossible with today's technology.

• Research with Bernhard Suhn showing that if factor in correction times, speech input may be slower and less natural than typing, etc.

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