Chapter 6 Direct Manipulation

1
Chapter 6 - Direct Manipulation Virtual
Environments

• Christopher Bunn Robert Stanley

2
Overview - Direct Manipulation Systems

• What does interactive systems generate to the
  users
• Mastery of the interface
• Competence in performing the task
• Retaining mastery over time
• Enjoyment in using the system
• Spread knowledge to novices
• Increase knowledge and explore the system

3
Command Interfaces (prompt-response)

• Advantages
• simple
• terse -- little typing
• feedback of dialog state
• commonality between interface and previous
  experience
• popular with computer experts
• immediacy of response
• allows parallel events to occur in dialog
• Disadvantages
• minimal feedback on system state
• encourages a mixture of interfaces from
  different applications
• impossible to refer to previously displayed
  information
• very underdetermined or overly secretive

4
Direct Manipulation Roots

• 1981 - Xerox STAR, Based on a physical office or
  desktop metaphor. It is a multifunctional system
  combining
• document creation, data processing, electronic
  filing, mailing, and printing. It adheres to a
  small set of design
• principles which make it seem familiar and
  friendly, simplify the HCI, unify its functions
  and allow transfer of
• experience.
• Shortly after Apple computers, Microsoft Windows
  and Hewlett Packard's New Wave OS.
• Hypermedia authoring tools such as HyperCard and
  ToolBook offered easy access to graphic tools,
• programmable buttons and other objects which
  facilitate rapid creation and revision or
  refinement of direct
• manipulation interfaces. Availability of such
  tools is a boon to hypermedia developers but
  leaves them with the
• challenge of determining what direct
  manipulation really means and how to go about
  designing good direct
• manipulation interfaces.
• Note Definitions of Direct Manipulation have
  generally not focussed on graphics. Direct
  Manipulation definitions
• were formulated before hypermedia tools were
  available to provide easy incorporation of
  elegant graphics with
• flexible point and click interactivity.

5
Direct Manipulation Defined

• Direct manipulation (Shneiderman 1982a) has
  become a popular concept in the
• user interface field for describing a certain
  class of interaction styles. Initially, the
• term was used to characterize entire applications
  in a strict classification scheme
• where a system was seen as either having a direct
  manipulation interface or
• belonging to some other category of interfaces
  like natural language, menu-driven,
• or form fill-in. This usage lead Wixon and Good
  (1987) to point out the apparent
• paradox of having several early "canonical"
  direct manipulation applications make
• heavy use of menus and form fill-in (dialog
  boxes).

6
Examples

• WIMPs/GUIs -- e.g. Macintosh desktop
• These have
• Multiple windows including different
• applications
• Icons for files, folders, applications
• Command selection via menus
• or keyboard
• Pointing device, usually a mouse
• Graphical and text display
• Advantages
• Easy to learn and use
• Switching applications is easy
• Full screen interaction supported
• Disadvantages
• complex
• need graphical display

7
Examples - Continued

• The SideKick control panel is a functional
  extension to the visual user interface presented
  by the
• Alladin or GeniePlus effects system. The
  SideKick allows you to, modify or review effects
  on the
• Alladin or GeniePlus systems with all of the ease
  traditional digital effects systems have enjoyed
  for
• many years. With the SideKick panel, the Alladin
  or GeniePlus truly enters the professional video
• and broadcast production environment, providing a
  user friendly control panel dedicated to the
• creation and manipulation of effects.

8
No Errors

• It is frequently claimed that direct manipulation
  interfaces reduce the need for error messages
• and this property was one of the main advantages
  listed in Shneiderman's original article
• defining the term (Shneiderman 1982a).
• As a matter of fact, errors frequently do occur
  when using direct manipulation systems but in
• many cases the error messages are pretty poor,
  maybe because the designers have believed
• the "no errors" claim. As an example, users of
  the Macintosh Finder file system interface very
• often get the error message "An Application
  could not be found for this Document." This error
• message succeeds in breaking almost all the
  standard principles for message design
• (Shneiderman 1982b) It uses computer-oriented
  terminology rather than user-oriented
• terminology, it is general rather than specific,
  and it is not constructive.

9
Directness Indirectness

• The very term "direct manipulation" implies some
  kind of directness in the user interface. Again,
  the layered
• protocol analysis indicates some modifications to
  this supposed advantage. As a matter of fact, it
  is possible for
• a direct manipulation interface to feel very
  indirect to the user on some levels of the
  dialogue.
• For example, setting a tabulator in one desktop
  publishing program requires the following series
  of steps
• 1.Call up the tabulator dialog box (shown above)
  by using the pull-down menu or pressing a
  function key.
• 2.Since the dialog box appears independently of
  the text it controls, the user will have to
  position the dialog box
• until it is next to the text. Otherwise it will
  be very hard to compare the tab setting with the
  text layout. It may
• also be necessary to scroll the tab ruler if the
  text line is wider than the dialog box.
• 3.Actually change the tab setting by dragging
  the tab indicator.

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WYSIWYG

• To achieve WYSIWYG (what you see is what you
  get), there should be a direct mapping between
  the goal state
• (what you want) and the syntax level (what you
  see). Remember that the syntax level contains the
  two
• dimensional layout of the dialogue elements on
  the screen. In a WYSIWYG interface, the screen
  representation
• of objects mirrors the real world, and the
  syntax of operations correspond to the desired
  real world action.
• Example, most mouse-based interfaces have a
  two-cursor problem (Brooks 1988) where one cursor
  is used to
• point and another cursor indicates where text
  input will appear. Users often confuse these two
  cursors because
• of the lack of WYSIWYG in the interface. The
  pointing cursor that tracks the user's mouse
  movements is the
• user's focus of attention ("what you see") in
  the syntax, but the input ("what you get")
  changes the output
• product according to the location of the
  insertion mark. One possible solution to the
  two-cursor problem is to
• follow a strict WYSIWYG interpretation of a
  single cursor where input appears wherever the
  pointer happens to
• be when the user hits the keyboard (Akscyn et
  al. 1988).
• Changing the headers in one early
  graphical-interface word processor required the
  user to open a special
• window for the header. The actual editing
  followed direct manipulation principles as
  defined here since there
• was a direct mapping between the syntax for
  changing the header and the semantic change in
  the stored
• header information. But the interaction
  technique was not WYSIWYG since the user could
  not easily translate
• between the syntax for changing the header and
  the goal of making the header look a specific way
  in relation
• to the rest of the page. For a true WYSIWYG
  editing of headers, it becomes necessary to make
  them editable in

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Direct manipulation (e.g. mouse)

• Advantages
• novices can learn basic functionality
  quickly
• experts can work extremely rapidly
• casual users can retain operational concepts
  
• error messages are rarely needed
• users can see if they are doing what they
  thought
• reversibility available (usually)
• users have reduced anxiety
• Disadvantages
• model specificity
• may limit attention to physical constraints
• repetitive operations are tedious
• may not conform to user expectations
• precision in manipulating objects required

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Visual Thinking Icons

• Icon is a Greek word that means Image.
• Icons aide in our Visual thinking - example
  scissors, clipboard, diskette, etc.
• Semiotics is the science of signs graphical,
  such as pictures verbal,
• writing or sounds or others such as body
  gestures and clothes.
• A few guidelines in designing Icons
• 1. Limit the number of different icons.
• 2. Represent the object in a familiar manner.
• 3. Icon should stand out from its background.
• 4. Design movement animation.
• 5. Detailed information - shading, thickness,
  and color.