3.1 Introduction

3.1.1 Definition

One of the biggest challenges in providing me-centric computing is the way that humans interact with computers. Interface design used to be machine-centered, so if something failed, it was the user's fault. Over time, people learned to complain about the design and blamed the designer. As a result, designers want to help the user. At this point, we have established a user-directed attitude, i.e., designing for the user . However, how to act on it is not entirely straightforward. Good intentions are not enough; the design and the design process must relate to the users somehow.

On one hand, it is important to accommodate the growing number of computer users whose professional schedules will not allow the elaborate training and experience that was once necessary to take advantage of computing. On the other hand, computers should become accessible to those who cannot afford these training courses. Increased attention to usability is also driven by competitive pressures for greater productivity, the need to reduce frustration, and to reduce overhead costs such as user training. As computing affects more aspects of our lives, the need for usable systems becomes even more important. There has been lots of effort going in this direction over the past fifty years , and it is known as "human-computer interaction" (HCI).

The ACM SIGCHI ^[1] defines HCI as follows : "Human-computer interaction is a discipline concerned with the design, evaluation, and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them."

^[1] Hewett, Baecker, Card, Carey, Gasen, Mantei, Perlman, Strong, and Verplank (1996). "ACM SIGCHI Curricula for Human-Computer Interaction".

To simplify, HCI's aim is to optimize the performance of human and computer together as a system. Human-computer interaction studies both the mechanism side and the human side of computing devices. As its name implies, HCI consists of three parts : you the user, the computer itself, and the ways you work together. In Table 3.1, you can see the key elements of HCI.

Table 3.1. Key Elements of HCI

If a system is designed well regarding its human-computer interfaces, it will include the following features:

• Learnability It is easy to learn how to use the system, and the learned skills are retained well over time.

• Throughput Tasks can be performed quickly (or only a few people are required to perform a task), and the user error rate is very low. Users and systems can recover from errors easily.

• Flexibility The system is suitable for the expertise of the intended users and can be customized to suit different ways of working and/or different levels of expertise.

• Attitude The users' subjective satisfaction with the system is high.

HCI not only looks at interfaces for individuals, but also for groups of humans and organizations; therefore, interfaces for distributed systems, computer-aided communications between humans, or the nature of the work being cooperatively performed by means of the system are also part of the considerations.

Design in HCI is more complex than in many other fields of engineering. HCI is an interdisciplinary area. It is emerging as a specialty concern within several disciplines, each with different emphases:

• computer science application design and engineering of human interfaces.

• psychology application of theories of cognitive processes and empirical analysis of user behavior.

• sociology and anthropology interactions between technology, work, and organization.

• industrial design development of interactive products.

Furthermore, the developer's task of making a complex system appear simple and sensible to the user is in itself a very difficult task.

From a computer science perspective, other disciplines serve as supporting disciplines, much as physics serves as a supporting discipline for civil engineering, or as mechanical engineering serves as a supporting discipline for robotics . A lesson learned repeatedly by engineering disciplines is that design problems have a context, and that the overly narrow optimization of one part of a design can be rendered invalid by the broader context of the problem.

Because human-computer interaction studies a human and a machine in communication, it draws from supporting knowledge on both the machine and the human side. On the machine side, techniques in computer graphics, operating systems, programming languages, and development environments are relevant. On the human side, communication theory, graphic and industrial design disciplines, linguistics , social sciences, cognitive psychology, and human performance are relevant. And, of course, engineering and design methods are relevant.

3.1.2 Roots of HCI

As discussed above, HCI arose as a field from intertwined roots in computer graphics, operating systems, human factors, ergonomics, industrial engineering, cognitive psychology, and the systems part of computer science. The first human-computer interaction techniques were introduced in the early days of computing, when systems first started using graphics in combination. Since then, interfaces and graphics have improved a lot. Today, we have algorithms and hardware that allow the display and manipulation of ever more realistic-looking objects (e.g., detailed buildings or images of body parts). Many fields in computer science have a natural interest in HCI. Just look, for example, at computer graphics, which sees HCI as "interactive graphics," allowing the user to manipulate solid models in a CAD system.

The roots of today's HCI go back quite some time. Have a look at the ubiquitous graphical interface used by Microsoft Windows, which is based on the Macintosh, which is based on work at Xerox PARC, which in turn is based on early research at the Stanford Research Institute (SRI) and at MIT. ^[2]

^[2] http://www.mit.edu/

In the 1960s, several research topics related to HCI were first investigated, related to HCI, such as the "man-machine symbiosis" and the " augmentation of human intellect." These research areas led to a number of important building blocks for human-computer interaction. These building blocks are all included in modern operating systems: a windowing system, the mouse, bitmapped displays, personal computers, the desktop metaphor, and point-and-click editors. These early developments led to operating systems with advanced techniques for interfacing input/output devices, for tuning system response time to human interaction times, for multiprocessing, and for supporting windowing environments and animation.

Closely related to HCI is the science of "human factors," a discipline derived from the problems of designing equipment operable by humans during World War II. Many problems faced by those working on human factors had strong sensory -motor features (e.g., the design of flight displays and controls). The problem of humans operating computers was a natural extension of classic human factors, except that the new problems had substantial cognitive, communication, and interaction aspects.

Ergonomics is similar to human factors. As with human factors, the concerns of ergonomics tended to be at the sensory-motor level, but with an additional physiological flavor and an emphasis on stress. Human interaction with computers was also a natural topic for ergonomics, but again, a cognitive extension to the field was necessary, resulting in the current "cognitive ergonomics" ^[3] and "cognitive engineering." ^[4] Because of their roots, ergonomic studies of computers emphasize the relationship to the work setting and the effects of stress factors, such as the routinization of work, sitting posture , or the vision design of CRT displays.

^[3] http://www.eace. info /

^[4] http://lorien.ncl.ac.uk/ming/resources/cal/cogsci.htm

In the early years of the 20th century, companies needed to raise productivity, which led to industrial engineering. Industrial engineering emphasized in the beginning improving manual methods of work, such as a two-handed method for laying bricks , instead of using only one. It also led to the design of specialized tools to increase productivity and reduce fatigue, such as brick pallets at waist height so bricklayers didn't have to bend over. Last, but not least, industrial design also led to the design of the social environment, such as the invention of the suggestion box. Interaction with computers is a natural topic for the scope of industrial engineering in the context of how the use of computers fit into the larger design of work methods.

At the end of the 19th century, cognitive psychology derived from attempts to study sensation experimentally. After World War II, cognitive psychology became an experimentally oriented discipline that is concerned with human information and performance. It has influences from linguistics, computer engineering, and communications engineering. Cognitive psychologists concentrate their research on the learning of systems, the transfer of that learning, the mental representation of systems by humans, and human performance on such systems.

Finally, the growth of discretionary computing and the mass personal computer and workstation computer markets have meant that sales of computers are more directly tied to the quality of their interfaces than in the past. The result has been the gradual evolution of a standardized interface architecture from hardware support of mice to shared window systems to "application management layers ." Along with these changes, researchers and designers have begun to develop specification techniques for user interfaces and testing techniques for the practical production of interfaces.

3.1.3 Me-Centric Interactions

Human-computer interaction is, in the first instance, affected by the forces shaping the nature of future computing. Among these forces are the decreasing hardware costs leading to faster systems with more memory. At the same time, the hardware is being miniaturized and requires less power, leading to more mobility. Through new output technologies, such as new displays and voice communication, computational devices change their form. At the same time, information technology is spreading into the environment, leading to many technologically enhanced devices at home and at work (e.g., VCRs become TiVo-like devices, microwave ovens become food management devices, washing machines become clothes management devices). Through specialized hardware, new functions (such as rapid text search) can be implemented easily.

New developments in infrastructure allow new forms of network communication and distributed computing. Through lower prices, reduced complexity of applications, and new input techniques, computers are increasingly widespread among people who are outside of the computing profession. These new input techniques also allow improved access to computers by currently disadvantaged groups, such as young children and the physically/visually disabled.

In the future, computers and smart appliances will communicate through high-speed local networks, nationally over wide-area networks, and portably via infrared, ultrasonic, cellular, and other technologies. Data and computational services will be portably accessible from many if not most locations to which a user travels .

Some of these new systems will have large numbers of functions associated with them. Some others will have fewer functions than typical desktop computers. And there surely will be so many systems that most users, technical or non-technical, will not have time to learn them in the traditional way (e.g., through thick manuals).

These systems will handle images, voice, sounds, video, text, and formatted data. These will be exchangeable over communication links among users. The separate worlds of consumer electronics (e.g., stereo sets, VCRs, televisions ) and computers will partially merge. Computer and print worlds will continue to cross-assimilate each other.

Computation will pass beyond desktop computers into every object for which uses can be found. The environment will be alive with little computations from computerized cooking appliances to lighting and plumbing fixtures to window blinds to automobile braking systems to greeting cards. To some extent, this development is already taking place. The difference in the future is the addition of networked communications that will allow many of these embedded computations to coordinate with each other and with the user. Human interfaces to these embedded devices will in many cases be very different from those appropriate to workstations.

Interfaces to allow groups of people to coordinate will be common (e.g., for meetings, for engineering projects, for authoring joint documents). These will have major impacts on the nature of organizations and on the division of labor. Models of the group design process will be embedded in systems and will cause increased rationalization of design.

Ordinary users will routinely tailor applications to their own use and will use this power to invent new applications based on their understanding of their own domains. Users will thus be increasingly important sources of new applications at the expense of generic systems programmers (with systems expertise but low domain expertise).

One consequence of the above developments is that computing systems will appear partially to dissolve into the environment and become much more intimately associated with their users' activities. One can make an analogy to the development of motion power. Once, strikingly visible, large, centralized water wheels were used to drive applications via belt drives ; now electric motors are invisibly integrated into applications from VCRs to refrigerators. Of course, this will not always be trouble-free. In Table 3.2, you will find some of the most common issues.

Table 3.2. Possible Issues with Smart Appliances

Product developers often incorporate multiple functions into a device to provide flexibility and to serve a wider user community. However, extensive functional capability may well impose an unreasonable cognitive load on the user, unless considerable effort is devoted to the design of the user interface. The following are some problems that apply to many devices and can lead to errors:

• Control Sequences Can be illogical or cumbersome

• Language, Prompts, Symbols, or Codes May be unfamiliar or missing

• Display Formats Inconsistencies may occur

• User Expectations Conventions may contradict

• Feedback Uncertain or no feedback after input

• Functionality May be hidden from the user

• Status Information May be missing

• Complex mental calculations Requirements may be unclear

Of course, personal computers in some form will continue to exist (although many might take the form of electronic notebooks ), and there will still be the problem of designing interfaces so that users can operate them. But the rapid pace of development means that the preparation of students must not only address the present state of technology, but also provide the foundations for future possibilities.

3.1.4 Human Characteristics

It is important to understand something about human information-processing characteristics, how human action is structured, the nature of human communication, and human physical and physiological requirements. There are many aspects that need to be considered when a human processes information.

The first issue is how people use their memory. The difference between short-term and long- term memory needs to be understood and how it can be achieved that important messages are saved correctly. The motor skills of the target group are also important. Interfaces should be designed in a way such that the target groups can easily operate them; although this may seem trivial, it provides a serious stumbling block for children or elderly people, if they have to use an interface designed by young people for young people.

Perception, attention, and vigilance also play an important role when designing good interfaces. Only if these aspects are taken into account can you make sure that the user is able to perceive the interface in the correct way and stay with it. If it is designed badly , the user may decide to abandon the interface and not execute the necessary task.

One should also not forget to take problem-solving skills into account when designing an interface. Technical people may be able to understand "error: 30" because they know the specification of the system, but if the target group consists of less technical people, one should create meaningful error messages and help the user to solve problems actively. The same is true for learning and skill acquisition. Depending on the user group, help should be provided appropriately. Only if this is done correctly can motivation of the users be improved, making the interface and its associated services and appliances successful.

On a more cognitive level, it is important to make sure that symbol-system and engineering models are applied correctly. Every culture has a different symbol-system relationship that needs to be taken into account. If the wrong symbols are used in the interface, it can cause a delay or a break in the process of using the interface. Therefore, it is important to understand the users' mental models and how they act. Fortunately, humans are diverse, which makes life more interesting. From a designer's point of view, this can be a nightmare, as this diversity needs to be accommodated in the interface systems.

Important aspects are language, communication, and interaction. Language is the communication and interface medium and needs to be taken into account when designing the interfaces. Therefore, it is important to understand such aspects of language as syntax, semantics, and pragmatics . Besides that, the formal models of language and pragmatic phenomena of conversational interaction, such as turn-taking and repair, need to be taken into account.

Over the last forty years, specialized languages, such as graphical interaction, query, command, production systems, and editors have been established and need to be revised to make them applicable for the next generation of smart appliances.