Direct Manipulation

  • When the virtual representation of an object is manipulated in a similar way to a real-world object
  • Proposed in 1983 by Ben Schneiderman
  • Can be traced back to Sketchpad (Ivan Sutherland)

Principles

  1. Continous representation of task objects and actions
  2. Objects are manipulated by physical actions, not comple syntax
  3. Fast, incremental, and reversible actions with effects on task objects immediately apparent
  4. Layer, self-revealing approach to learning

Benefits

  • User feel as if they are interacting with the domain rather than the interface
  • User can focus on task rather than the technology

Why it's not always used

  • Many commands are invoked indirectly
    • Menus, dialog boxes, toolbars
  • Many objects of interest are hidden
    • Text styles, page layout
  • many objects in the interface are not objects of interest
    • Toolbar palettes

Look and Feel

Look - how manipulatable objects are presented in the interface

Feel - how user expression is translated into commands to manipulate objects

Interaction Model

  • By Lafon, 2000
  • A set of principles, rules and properties that guide the design of an interface
  • Describes how to combine interaction techniques that defines the look and feel
  • Can be used to evaluate specific interaction designs

Instrumental Interaction

  • A model of interaction based on how we naturally use tools to manipulate objects in the real world

Interaction instrument - a necessary mediator between the user and domain objects

Domain objects - he thing of interest, data and associated attributes, which is manipulated using an interaction instrument

Instrument activation - when instrument is under user's control

  • WIMP instruments activated spatially and temporally

Refication and Meta-Instruments

Reification - turning concepts into something concrete

  • An instrument is the reification of a command; scrollbar => reifies scroll commands

Meta-instrument - an instrumnet that acts on another instrument

  • The other instrument becomes an object of interest
  • e.g. pencil is an instrument to manipulate the object "paper"; when the pencil breaks, it becomes an object of interest to be manipulated by the sharpener meta-instrument

Object Reification - turning attributes of a primary object into other objects of interest

Evaluating Instrument

Degree of indirection - spatial/temporal offset between instrument and action on object

  • 2D measure of spatial and temporal offsets of instrument
  • Spatial dimension
    • e.g. _near: _drag to translate, handles on to resize
    • e.g. med: scrollbars
    • e.g. far: dialog boxes
  • Temporal dimension
    • e.g. short: direct dragging response
    • e.g. med: activate tool in toolbar, the start direct manipulation
    • e.g. long: using dialog, finishing drag-and-drop

Degree of integration - ratio of degrees of freedom of instrument to degrees of freedom of input device

Degree of Compatibility - the similarity between the physical actions on the instrument and the response of the object

Direct Manipulation and Instrumental Interaction

  • Direct manipulation interface allows a user to directly act on a set of objects in the interface

  • Direct means instruments are visually indistinguishable from objects they control

    • Actions on instrument/object entities are analogous to actions on similar objects in real world
    • Actions on instrument/object entities preserve the conceptual linkage between instrument and object

  • Should build on existing experiences and intuitions to aid learning

    • e.g. trash bin in OS and the real world

Direct Manipulation Issues

  • Visually impared users can't see graphics
  • Consumes valuable screen space
  • Switching between keyboard and pointer is time consuming
  • Analogies may not be clear
    • Users need to learn meaning of visual representations, which may be misleading

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