Human-computer interaction

In the section covering The COOPerator, I state my assignment within the project: designing COOPerator's human-computer interface and implementing the design into the first prototype. This part of my thesis is concerned with human-computer interaction in general and human-computer interfaces in particular.

Human-computer interaction and interfaces

Preece [1993] mentions that human-computer interaction (or HCI) is a rapidly developing field. It considers problems related to the usability of systems. According to Nielsen [1993], usability is associated with these five usability attributes:

• Learnability: The system should be easy to learn so that the user can rapidly start getting some work done with it.
• Efficiency: The system should be efficient to use, so that once the user has learned the system, a high level of productivity is possible.
• Memorability: The system should be easy to remember, so that the casual user is able to return to the system after some period of not having used it, without having to learn everything all over again.
• Errors: The system should have a low error rate, so that users make few errors during the use of the system, and so that if they do make errors they can easily recover from them. Further, catastrophic errors must not occur.
• Satisfaction: The system should be pleasant to use, so that users are subjectively satisfied when using it; this means that they like it.

To a large extent, the human-computer interface of an information system determines its usability. Other factors probably include the computer on which the system is used (e.g., is it fast or slow), general ergonomic factors (e.g., the right position or chair and how long the work is done in succession), or perhaps even the work climate.

Before I present my own definition of a human-computer interface, I offer you an outline of this section.

Contents of this section

To start with, I sketch the short history of human-computer interaction. Many other technological developments involve the replacement of older technology with newer inventions, but a good designer of modern human-computer interfaces still needs to know how to best use interaction techniques from several generations ago (Nielsen).

The remainder of this section is mostly concerned with topical subjects in human-computer interface design. As a matter of fact, the definition presented later on this page is expressed in terms of these topics. User-centered interface design is dealt with first. Next, object oriented interfaces and direct manipulation are braught up. Finally, metaphors are discussed.

A special kind of metaphor, the hypertext model, is examined in a separate subsection because of its great importance in the context of cooperative work. Finally, the impact or influence of cooperative work on interfaces is presented.

Interface defined

Probably, you intuitively know what a human-computer interface is. And the following description is perhaps characteristic of how you would describe an interface:

The basic user interface is usually understood to include things like menus, windows, the keyboard, the mouse, the 'beeps' and other sounds the computer makes, and in general, all the information channels that allow the user and the computer to communicate. (Lewis and Rieman [1993])

In my opinion, this description of an interface is not accurate enough. It mentions communication between human and computer, yet it does not mention any goal for this communication. Apparently, a human interacts with the computer by tapping a keyboard or by choosing options from menus with a mouse. But what does he respond to? How is meaningful information communicated back to the user? What happens whenever he performs an action? Compare this definition to the following.

Interface redefined

In my opinion, a human-computer interface can be described using topical subjects:

• is a distinctive part of a computer application which is focused on interaction with humans;
• is user-centered, hence task-oriented (although still constrained by the application model);
• applies the notion of common ground and tries to establish this feeling during the interaction process;
• uses direct manipulation of objects as the primary interaction technique;
• the user is familiar with the objects; he either knows them from the real world or comprehends the mental model of the objects.

These principles are all somewhat abstract and may even seem inpractical or unreachable at this time. However, in my opinion, they serve as a fine higher level frame of reference for the human-computer interface designer.

Thus, a human-computer interface would be:

the part of a computer program responsible for establishing the common ground with a particular (i.e. well-known) user. His task is accomplished by expanding and maintaining this common ground throughout the interaction process with the application. Whenever possible, direct manipulation of familiar objects should be the leading interaction principle.

I encourage you to follow the hyperlinks on this page to explore these topical design principles and find the answers to the before mentioned questions!