Direct Manipulation - Introduction Imagine driving a car that has no steering wheel, accelerator, brake pedal... In place of the familiar manual controls, you have only a keyboard for input. You could drive by typing in commands such as "slow to 20 and turn left" What makes real cars easier to drive is the directness of their controls. Each interface is specially designed for controlling some function. Our computer car has only one control - a keyboard.
Graphic (DM) Interaction Overview Tools for the development of graphical or direct manipulation interfaces are part of many window toolkits. Their implementation is most often based on the object-oriented paradigm where graphical objects represented by icons are acted on by events caused by the user, the application, or other objects.
DM Examples (1) Display editors Appear of the full screen (as opposed its line- oriented) WordStar, Word, EMACS, vi, LSE, MacWriter. These products are often described as WYSIWYG (What you see is what you get). To boldface in WYSIWYG you select the text and boldface. In a non-display editor, the text to be boldfaced would be tagged (eg. With a “.bf” tag). Cursor oriented for positioning instead of following the linear sequence of lines. Immediate display of results(action) Actions are easy to reverse
DM Examples (2) Spread sheets, video games e.g. use "paddles" to hit "ball""frog jumps across road" easy to learn- but can become more skilled with practice challenging and useful to advance users as well no syntax no error messages Provide immediate feedback to user input.
DM Advantages Some data suggests that graphical computer objects are easier to remember and use than keystroke objects (Cuniff & Taylor, 1987).
Direct manipulation systems have four features: continuous representation of objects and actions of interest. physical actions or labeled button presses manipulate objects and initiate actions. impact of actions on objects is immediately visible. data objects selected and operated on by simulated physical control instead of by verbal reference (eg. that one not the one in row 6).
Where did idea of DM UI's come from Influences, philosophies grow out of UI for Xerox STAR, circa 1970's: for the user, a familiar conceptual model, the desktop, made of icons and windows. ability to see and point rather than remember and type WYSIWYG universal commands across applications, such as MOVE, COPY, DELETE
STAR failed in marketplace. most users were still professional programmers who did not appreciate the interface. cost $15,000. little useful software lacked an open architecture. Third party vendors could not write s/w for the STAR. perceived as slow.
DM Issues to Consider. There are degrees of directness. The roles of space and motion of objects is not well-understood. Choice of symbols or icons - must be meaningful to all. Taking actions from keyboard to use mouse is distracting.
DM Guidelines Graphical representation should be appropriate and meaningful (based on user feedback) Possible that user could add a new or compound object or action.