Direct Manipulation
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Introduction
Direct manipulation is the visual representation of the world of actions. For example, the desktop metaphor (Microsoft Windows) which the user can manipulate. Direct manipulation is one of the primary interaction styles which has been used by designers and programmers for their systems. Direct manipulation allows novice users access to powerful instructions without the trouble of learning how to use a complex syntax and/or an extensive list of commands.
Direct manipulation involves three interconnected techniques:
- Provide a physically direct way of moving a cursor or manipulating the objects of interest.
- Present a concrete visual representation of the objects of interest and immediately change the view to reflect operations.
- Avoid using command language and depend on operations applied to the cognitive model which is represented on the display.
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History
Direct manipulation is considered to be one of the most significant achievements in Human Computer Interaction (HCI) theory and design. The term was first introduced in the 1980's by Ben Shneiderman, however the desktop metaphor was introduced first by Alan Kay at Xerox PARC in 1970.
Shneiderman published a paper in 1983 titled "Direct Manipulation: A step beyond programming languages" in which he noted the appeal of manipulating graphically represented objects instead of formulating complex linguistic commands.
He characterized this style of interaction by three properties:
- Continuous representation of object of interest.
- Physical actions or labeled buttons pressed instead of the use of syntax
- Rapid incremental reversal of actions with an immediate impact on object of interest.
The paper began with two examples of office applications: word processing and spreadsheet. The ability to display the final form on the screen, move a cursor by arrow keys, see the results of an action immediately and to easily reverse commands. Novice users would also enjoy using direct manipulation software because they can rapidly master the system within a short period of time.
He also proposed that testing should be done before introducing direct manipulation systems to ensure proper behaviour of the system, especially if uncommon metaphors are being used.
Shneiderman mentioned in his paper that direct manipulation isn't without its faults. He said that using spatial or graphical representation doesn't necessary improve performance. He identified the following four problems with direct manipulation:
- Cluttered presentation can lead to greater confusion
- Users have to learn the meaning of the graphically represented components
- Graphical representation can be misleading
- Representation may take excessive screen space
This concept witnessed a hugely beneficial impact on personal computing and plays a major role in modern interactive software design.
Advantages
- Visually presented task concepts, for example if the user wants to discard or delete a file, then he/she simply selects the object and then presses the delete key. This action sends the object to the recycling bin and can be disposed at a later time. This task concept of discarding unwanted material to the recycling bin is visually analogous to how humans throw away trash in a trash can.
- Allows easy learning for a first time user. Direct manipulation has an easy learning curve, since tasks done on the computer are related to tasks in the real world. This direct approach makes the operations done on the computer easier to understand for a new user.
- Allows easy retention since tasks done through direct manipulation are similar to real world tasks. Therefore, it is easy to retain operations learned on the computer. For example, the copy and paste operation executed on the computer can easily be retained because it is similar to the action of photocopying a document in the physical world.
- Allows errors to be avoided since direct manipulation does not allow some incorrect actions, for example when using drag-and-drop the cursor changes shape to a no access image when an action cannot be executed. This minimizes the chance of the user making errors in performing computer related tasks.
- Encourages exploration because of easy navigation through graphical icons and other visual representation techniques. As a result, this makes it easy for the user to explore through the computer applications.
Disadvantages
- May be hard to program because some tasks may be easy to do in the real world but difficult to mimic through software and/or computer operations. For example playing a complex game where strategy is a prime factor, like chess, is somewhat easier to do in real life than to program how a player will make their next chess piece move.
- May require graphics displays & pointing device(s), for example if the computer does not have a mouse connected to it. Drag and drop operations done on the computer may be more difficult to perform.
Importance to CHI
Direct manipulation depends on visual representation of the objects and actions of interest. In other words, physical actions or pointing instead of complex syntax. Operations whose effect on the object of interest is immediately visible. When users can specify what they want with clear and conceivable actions selected from a visual display, then they can more frequently succeed in finishing their task, whilst maintaining a sense of control. Also, with this method users can feel directly responsible for their actions and acquire a sense of accomplishment.
Currently, with user interfaces allowing zooming, drag and drop capabilities, etc., users are exposed to more engaging and more capable user interfaces. Direct Manipulation is leading designers to produce interfaces that are more understandable, predictable and manageable.
References
- Dr.Poehlman. Software Engineering 4DO3/6D03 Computer Science 4HC3, Fall 2009, McMaster University Courseware, Lecture Notes.
- Preece, Jennifer J., Rogers, Yvonne, Sharp, Helen and Benyon, David (1994): Human-Computer Interaction. Essex, UK, Addison-Wesley Publishing
- Shneiderman, Ben (1982): The Future of Interactive Systems and the Emergence of Direct Manipulation. In Behaviour and Information Technology, 1 (3) pp. 237-256
- Shneiderman, Ben (1983): Direct manipulation: A step beyond programming languages. In IEEE Computer, 16 (8) pp. 57-69
- Sutherland, Ivan E. (1963): Sketchpad: A man-machine graphical communication system. In: Proceedings of the AFIPS Spring Joint Computer Conference 1963. pp. 329-346.
