Direct Manipulation User Interfaces

User Interface Styles

• Menus
• Forms
• Command language
• Direct manipulation (GUI and WIMP)

Direct Manipulation Interface Characteristics

• Screen objects resemble physical objects
• Objects arranged in 2-D space
• Trades perceptual motor operations for linguistic operations
• Use of recognition in place of recall
• Expensive to implement

Direct Manipulation Interface Examples

• Display editors and word processors
• Spreadsheet programs
• Spatial and geographic databases
• Video games and educational simulations
• CAD and paint type applications
• Hypertext
• Office automation software
• Virtual reality

Advantages of WYSIWYG Word Processors

• Displays full page of text
• Displays document in preview format
• Shows cursor to user
• Control cursor using intuitively obvious moves
• Use labeled icons for actions
• Display results of actions immediately
• Provide rapid display response
• Offers easily reversible actions

WP Works Spawned Other Developments

• Integration of multimedia and hypermedia with text documents
• Desktop publishing tools
• Slide presentation software
• Hypermedia environments
• Improved macro facilities
• Spellcheckers and thesauri
• Grammar checkers
• Document assemblers

GOMS Model for Direct Manipulation Interfaces

Basic goal - minimize learning using a metaphoric device

Basic method - find relevant object on screen and manipulate

Step 1. Search screen for an object to operate on

Step 2. Select it for manipulation

Step 3. Move object on screen to destination

Must ensure:

• Visual search (steps 1 and 3) works easily to find objects and their destinations
• Steps 2 and 3 must be fast consistent and easy to learn
• There must be a familiar direct manipulation metaphor or analogy (e.g. desktop)

Problems with Direct Manipulation Interfaces

• Visual representations are more spread out than simple text - causing "off page" problems
• Users must learn meaning of components (e.g. icons) which are meaningful to designer and not user
• Visual representation may be misleading
• Touch typists do better with a keyboard than with a mouse

Direct Manipulation Interfaces Allow:

• Novices to learn basic fundamentals quickly
• Experts to carry out new tasks
• Knowledgable intermittent users to retain operational concepts
• Error messages are rarely needed
• Users can assess progress to goals and make changes instantly
• Users experience less anxiety because systems is understood and actions are reversible
• Users gain confidence and mastery through their sense of control over the system

The debate concerning text versus icons is an emotional one (depends on how quickly user can figure out meaning of icon).

Icon Design Guidelines

• Represent object/action in recognizable form
• Limit number of icons
• Make icon stand out from background
• Be careful when using 3-D icons
• Selected icons must be easily distinguished from unselected icons
• Icons unique from one another
• Ensure harmony with family of icons
• Design animation movement
• Add detailed information if possible
• Explore use of icon combinations to create new objects or operations

Marcus - Icon Design Considerations

• Lexical qualities (shape, color, brightness)
• Syntactics (appearance and component movement)
• Semantics (concrete vs abstract representation)
• Pragmatics (overall subjective impression)
• Dynamics (e.g. receptivity to mouse operations)

Five Challenges of Direct Manipulation Programming

• Sufficient computational generality
• Access to appropriate data
• Ease in programming an editing
• Simplicity in subprogram invocation and assignment of arguments
• Low risk

Growth Areas for Direct Manipulation Interfaces

• Home automation
• Remote direct manipulation
• Virtual reality

Components for Successful VR Application

• Visual display
• Head positioning and sensing
• Hand positioning and sensing
• Force feedback
• Sound input/output
• Other sensation
• Cooperative and competitive VR

Direct Manipulation Concerns

• Increased system resources
• Cumbersome actions
• Weak macro techniques
• History tracing is hard to log
• Visually impaired users at risk