Direct Manipulation

The central ideas of direct manipulation are visibility of objects and actions of interest; rapid, reversible, incemental actions; and replacement of command-language syntax by direct manipulation of the object of interest.

Examples

Display editors and word processors
Visicalc and its descendents
Spatial Data management, eg geographic applications
Video Games
CAD/CAM
Query by example (forms)

The key to direct manipulation is to come up with an appropriate representation or model of reality. It is essential to think visually. Try to conjure up a sequence of images rather than thinking in terms of a sequnce of instructions.

All is not wonderful however. There are space problems. Pseudo code is often better than flow charts. Sometimes the visual represnetation may be misleading in that the analogy may be imperfect (dragging a disk to the trashcan to eject it for example may suggest that something more final will in fact happen).

The Semantic-syntactic object-action explanation of the effectiveness of direct manipulation is that the object is displayed so that actions are directly in the high level task domain. Thus the user does not need to grapple with the syntax or semantics of using the computer and can concentrate on the task semantics.

Icons

Icons are appropriate where the task is visual since the user is cognitivell tuned to pictures. In an application that is text oriented icons may be less effective.

Icon Guidelines

Represent the object in a familiar and recognizable manner.
Limit the number of different icons
Make the icon stand out form its background
Three dimensional icons are eye catching but also distracting
Ensure that a single selected icon is clearly visible when surrounded by unselected icons
Make each Icon distinct form every other icon
Ensure the harmoniousness of each icon in a family
Design the movement animation when an icon is dragged and dropped
Add detailed information to the icon where possible, for example size can be coded in the icon or age by color
Comnitaions of icons (eg dragging a file to a printer) to describe actions.