Human-computer interface design is a new discipline. So new in fact, that Alan Kay of Apple Computer quipped that people "are not sure whether they should order it by the yard or the ton"! Irrespective of the measure, interface design is gradually emerging as a much-needed and timely approach to reducing the awkwardness and inconveniences of human-computer interaction. "Increased cognitive load", "bewildered and tired users" - these are the byproducts of the "plethora of options and the interface conventions" faced by computer users. Originally, computers were "designed by engineers, for engineers". Little or no attention was, or needed to be, paid to the interface. However, the pervasive use of the personal computer and the increasing number and variety of applications and programs has given rise to a need to focus on the "cognitive locus of human-computer interaction" i.e. the interface.

What is the interface? Laurel defines the interface as a "contact surface" that "reflects the physical properties of the interactors, the functions to be performed, and the balance of power and control." (p.xiii) Incorporated into her definition are the "cognitive and emotional aspects of the user's experience". In a very basic sense, the interface is "the place where contact between two entities occurs." (p.xii) Doorknobs, steering wheels, spacesuits-these are all interfaces. The greater the difference between the two entities, the greater the need for a well-designed interface. In this case, the two very different entities are computers and humans. Human-conputer interface design looks at how we can lessen the effects of these differences. This means, for Laurel, empowering users by providing them with ease of use. "How can we think about it so that the interfaces we design will empower users?" "What does the user want to do?" These are the questions Laurel believes must be asked by designers. These are the questions addressed directly and indirectly by the approximately 50 contributors to The Art of Human-Computer Interface Design.

In spite of the large number of contributors to the book and the wide range of fields with which they are associated, there is a broad consensus on how interfaces can be designed for empowerment and ease of use. User testing, user contexts, user tasks, user needs, user control: these terms appear throughout the book and suggest ways in which design might focus less on the technology and more on the user. With this perspective in mind, contributor D. Norman argues that computer interfaces should be designed so that the user interacts more with the task and less with the machine. Such interfaces "blend with the task", and "make tools invisible" so that "the technology is subervient to that goal". Sellen and Nicol insist on the need for interfaces that are 'simple', 'self-explanatory', 'adaptive' and 'supportive'. Contributors Vertelney and Grudin are interested in interfaces that support the contexts in which many users work. They consider ways in which group-oriented tasks and collaborative efforts can be supported and aided by the particular design of the interface. Mountford equates ease of use with understating the interface: "The art and science of interface design depends largely on making the transaction with the computer as transparent as possible in order to minimize the burden on the user".(p.248)

Mountford also believes in "making computers more powerful extensions of our natural capabilities and goals" by offering the user a "richer sensory environment". One way this can be achieved according to Saloman is through creative use of colour. Saloman notes that colour can not only impart information but that it can be a useful mnemonic device to create associations. A richer sensory environment can also be achieved through use of sound, natural speech recognition, graphics, gesture input devices, animation, video, optical media and through what Blake refers to as "hybrid systems". These systems include additional interface features to control components such as optical disks, videotape, speech digitizers and a range of devices that support "whole user tasks". Rich sensory environments are often characteristic of game interfaces which rely heavily on sound and graphics. Crawford believes we have a lot to learn from the design of games and that they incorporate "sound concepts of user interface design". He argues that "games operate in a more demanding user-interface universe than other applications" since they must be both "fun" and "functional".

Not only can designers learn from games, they can also draw on and use existing techniques from filmmaking, animation and storytelling. A. Don has investigated "the characteristics of oral storytelling and multimedia interface design". He encourages designers to "adopt strategies from narrative theory such as including multiple representations of events and information" and "using characters to convey information". Use of storytelling in design can provide ease of use because it takes advantage of user's prior knowledge. Another device for providing the user with familiar elements is that of metaphor. Oren remarks that metaphors are ubiquitous in computer use: "We place windows on our desktop, the put folders within the windows thus forming a tree.(p.472) Erickson posits that "a good metaphor is essential to an easy-to-use human interface" because it allows us "to take our knowledge of familiar objects and events and use it to give structure to abstract, less well understood concepts." (p.73) Blake sees metaphors in interface design as a means to allow people to "understand and to predict system behaviour" and as a "convenient means of portraying system attributes and operational tools in a way that does not require technical knowledge".

Use of metaphors, techniques from computer games , rich sensory environments, user control: these are just some of the many angles from which interface design is discussed in The Art of Human-Computer Interface Design. Approaches, perspectives and techniques may vary. Nonetheless, certain principles as well as challenges remain. "Interface design is hard" Erikson notes, because solutions are almost always compromises and because there will always be tradeoffs between speed and intuitiveness. To face the challenges, the design process needs to move towards a more multidisciplinary approach. The job can no longer be completed by a computer scientist, programmer or engineer working alone. Others must become involved in the process. "Psychologists, graphic designers, writers, industrial designers, and programmers all have essential contributions to make to the design of an interface" argues Erickson. "Yet each discipline has its own priorities and perspectives, its own methods, its own criteria for success. Often these are in conflict with one another." (p.3) Oddly enough, design problems that were once purely technical have become strongly political. Challenges that are often thought of as being related to design are frequently, in essence, professional and personal challenges. Facing all these challenges, be they technical or otherwise, is one of the many tasks that are part of the new discipline of human-computer interface design.

DISCUSSION
Computers are undoubtedly the most powerful mind tools that humans have at their disposal. They are also, however, extremely complex. Furthermore, the functions they perform, the speeds at which the operate and the data they can store are increasing at an exponential rate thus rendering them yet more complex. Ironically, as computers increase in complexity, they are becoming easier to use. This ease of use is made possible by the interface which presents a facade or illusion of simplicity. The interface translates, negotiates and intervenes on behalf of the user. It communicates with the programme which in turn communicates with the bits and bytes which in turn toggle the switches in the complex circuitry of the computer hardware. The mere stroke of a key or the click of a mouse sets in motion an almost infathomable, uncountable number of operations that are both invisible and unknown to the user.

Thus, the interface not only allows us to interact with the computer, it also allows us to control it. Laurel focuses on this essential issue in interface design when she uses the terms 'control' and 'power'. How can we make the interface more powerful and more empowering? The Art of Human-Computer Interface Design presents a coherent and effective set of answers to this question. One perspecitve on design that was reflected in the writings of many contributors was the need to focus on the user and on the tasks to be performed. And, as many of the contributors noted, to do this we can no longer rely only on science and technique. While computer hardware design may still be the exclusive domain of the engineer or scientist, interface design requires imaginative and creative solutions that cannot be inspired by science alone. Metaphors, games, rich sensory environments, virtual realities, illusion? Such is the stuff that art is made of. The title of Laurel's book expresses succinctly the essence of the new, emerging discipline which is that interface design is very much an art.