The first reports of skin complaints among people working with or near VDUs came from Norway as early as 1981. A few cases have also been reported from the United Kingdom, the United States and Japan. Sweden, however, has provided many case reports and public discussion on the health effects of exposure to VDUs was intensified when one case of skin disease in a VDU worker was accepted as an occupational disease by the Swedish National Insurance Board in late 1985. The acceptance of this case for compensation coincided with a marked increase in the number of cases of skin disease that were suspected to be related to work with VDUs. At the Department of Occupational Dermatology at Karolinska Hospital, Stockholm, the caseload increased from seven cases referred between 1979 and 1985, to 100 new referrals from November 1985 to May 1986.

Despite the relatively large number of people who sought medical treatment for what they believed to be VDU-related skin problems, no conclusive evidence is available which shows that the VDUs themselves lead to the development of occupational skin disease. The occurrence of skin disease in VDU-exposed people appears to be coincidental or possibly related to other workplace factors. Evidence for this conclusion is strengthened by the observation that the increased incidence of skin complaints made by Swedish VDU workers has not been observed in other countries, where the mass media debate on the issue has not been as intense. Further, scientific data collected from provocation studies, in which patients have been purposely exposed to VDU-related electromagnetic fields to determine whether a skin effect could be induced, have not produced any meaningful data demonstrating a possible mechanism for development of skin problems which could be related to the fields surrounding a VDU.

Case Studies: Skin Problems and VDUs

Sweden: 450 patients were referred and examined for skin problems which they attributed to work at VDUs. Only common facial dermatoses were found and no patients had specific dermatoses that could be related to work with VDUs. While most patients felt that they had pronounced symptoms, their visible skin lesions were, in fact, mild according to standard medical definitions and most of the patients reported improvement without drug therapy even though they continued to work with VDUs . Many of the patients were suffering from identifiable contact allergies, which explained their skin symptoms . Epidemiological studies comparing the VDU-work patients to a non-exposed control population with a similar skin status showed no relationship between skin status and VDU work. Finally, a provocation study did not yield any relation between the patient symptoms and electrostatic or magnetic fields from the VDUs (Wahlberg and Lidén 1988; Berg 1988; Lidén 1990; Berg, Hedblad and Erhardt 1990; Swanbeck and Bleeker 1989).In contrast to a few early nonconclusive epidemiological studies (Murray et al. 1981; Frank 1983; Lidén and Wahlberg 1985), a large-scale epidemiological study (Berg, Lidén, and Axelson 1990; Berg 1989) of 3,745 randomly selected office employees, of whom 809 persons were medically examined, showed that while the VDU-exposed employees reported significantly more skin problems than a nonexposed control population of office employees, upon examination, they were not actually found to have no more visible signs or more skin disease.

Wales (UK): A questionnaire study found no difference between reports of skin problems in VDU workers and a control population (Carmichael and Roberts 1992).

Singapore: A control population of teachers reported significantly more skin complaints than did the VDU users (Koh et al. 1991).

It is, however, possible that work-related stress could be an important factor that can explain VDU-associated skin complaints. For example, follow-up studies in the office environment of a subgroup of the VDU-exposed office employees being studied for skin problems showed that significantly more people in the group with skin symptoms experienced extreme occupational stress than people without the skin symptoms. A correlation between levels of the stress-sensitive hormones testosterone, prolactin and thyroxin and skin symptoms were observed during work, but not during days off. Thus, one possible explanation for VDU-associated facial skin sensations could be the effects of thyroxin, which causes the blood vessels to dilate (Berg et al. 1992).

Back

Introduction

Computers provide efficiency, competitive advantages and the ability to carry out work processes that would not be possible without their use. Areas such as manufacturing process control, inventory management, records management, complex systems control and office automation have all benefited from automation. Computerization requires substantial infrastructure support in order to function properly. In addition to architectural and electrical changes needed to accommodate the machines themselves, the introduction of computerization requires changes in employee knowledge and skills, and application of new methods of managing work. The demands placed on jobs which use computers can be very different from those of traditional jobs. Often computerized jobs are more sedentary and may require more thinking and mental attention to tasks, while at the same time require less physical energy expenditure. Production demands can be high, with constant work pressure and little room for decision-making.

The economic advantages of computers at work have overshadowed associated potential health, safety and social problems for workers, such as job loss, cumulative trauma disorders and increased mental stress. The transition from more traditional forms of work to computerization has been difficult in many workplaces, and has resulted in significant psychosocial and sociotechnical problems for the workforce.

Psychosocial Problems Specific to VDUs

Research studies (for example, Bradley 1983 and 1989; Bikson 1987; Westlander 1989; Westlander and Aberg 1992; Johansson and Aronsson 1984; Stellman et al. 1987b; Smith et al. 1981 and 1992a) have documented how the introduction of computers into the workplace has brought substantial changes in the process of work, in social relationships, in management style and in the nature and content of job tasks. In the 1980s, the implementation of the technological changeover to computerization was most often a “top-down” process in which employees had no input into the decisions regarding the new technology or the new work structures. As a result, many industrial relations, physical and mental health problems arose.

Experts disagree on the success of changes that are occurring in offices, with some arguing that computer technology improves the quality of work and enhances productivity (Strassmann 1985), while others compare computers to earlier forms of technology, such as assembly-line production that also make working conditions worse and increase job stress (Moshowitz 1986; Zuboff 1988). We believe that visual display unit (VDU) technology does affect work in various ways, but technology is only one element of a larger work system that includes the individual, tasks, environment and organizational factors.

Conceptualizing Computerized Job Design

Many working conditions jointly influence the VDU user. The authors have proposed a comprehensive job design model which illustrates the various facets of working conditions which can interact and accumulate to produce stress (Smith and Carayon-Sainfort 1989). Figure 1 illustrates this conceptual model for the various elements of a work system that can exert loads on workers and may result in stress. At the centre of this model is the individual with his/her unique physical characteristics, perceptions, personality and behaviour. The individual uses technologies to perform specific job tasks. The nature of the technologies, to a large extent, determines performance and the skills and knowledge needed by the worker to use the technology effectively. The requirements of the task also affect the required skill and knowledge levels needed. Both the tasks and technologies affect the job content and the mental and physical demands. The model also shows that the tasks and technologies are placed within the context of a work setting that comprises the physical and the social environment. The overall environment itself can affect comfort, psychological moods and attitudes. Finally, the organizational structure of work defines the nature and level of individual involvement, worker interactions, and levels of control. Supervision and standards of performance are all affected by the nature of the organization.

Figure 1. Model of working conditions and their impact on the individual

This model helps to explain relationships between job requirements, psychological and physical loads and resulting health strains. It represents a systems concept in which any one element can influence any other element, and in which all elements interact to determine the way in which work is accomplished and the effectiveness of the work in achieving individual and organizational needs and goals. The application of the model to the VDU workplace is described below.

Environment

Physical environmental factors have been implicated as job stressors in the office and elsewhere. General air quality and housekeeping contribute, for example, to sick building syndrome and other stress responses (Stellman et al. 1985; Hedge, Erickson and Rubin 1992.) Noise is a well-known environmental stressor which can cause increases in arousal, blood pressure, and negative psychological mood (Cohen and Weinstein 1981). Environmental conditions that produce sensory disruption and make it more difficult to carry out tasks increase the level of worker stress and emotional irritation are other examples (Smith et al. 1981; Sauter et al. 1983b).

Task 

With the introduction of computer technology, expectations regarding performance increase. Additional pressure on workers is created because they are expected to perform at a higher level all the time. Excessive workload and work pressure are significant stressors for computer users (Smith et al. 1981; Piotrkowski, Cohen and Coray 1992; Sainfort 1990). New types of work demands are appearing with the increasing use of computers. For instance, cognitive demands are likely to be sources of increased stress for VDU users (Frese 1987). These are all facets of job demands.

Electronic Monitoring of Employee Performance

The use of electronic methods to monitor employee work performance has increased substantially with the widespread use of personal computers which make such monitoring quick and easy. Monitoring provides information which can be used by employers to better manage technological and human resources. With electronic monitoring it is possible to pinpoint bottlenecks, production delays and below average (or below standard) performance of employees in real time. New electronic communication technologies have the capability of tracking the performance of individual elements of a communication system and of pinpointing individual worker inputs. Such work elements as data entry into computer terminals, telephone conversations, and electronic mail messages can all be examined through the use of electronic surveillance.

Electronic monitoring increases management control over the workforce, and may lead to organisational management approaches that are stressful. This raises important issues about the accuracy of the monitoring system and how well it represents worker contributions to the employer’s success, the invasion of worker privacy, worker versus technology control over job tasks, and the implications of management styles that use monitored information to direct worker behaviour on the job (Smith and Amick 1989; Amick and Smith 1992; Carayon 1993b). Monitoring can bring about increased production, but it may also produce job stress, absences from work, turnover in the workforce and sabotage. When electronic monitoring is combined with incentive systems for increased production, work-related stress can also be increased (OTA 1987; Smith et al. 1992a). In addition, such electronic performance monitoring raises issues of worker privacy (ILO 1991) and several countries have banned the use of individual performance monitoring.

A basic requirement of electronic monitoring is that work tasks be broken up into activities that can easily be quantified and measured, which usually results in a job design approach that reduces the content of the tasks by removing complexity and thinking, which are replaced by repetitive action. The underlying philosophy is similar to a basic principle of “Scientific Management” (Taylor 1911) that calls for work “simplification.”

In one company, for example, a telephone monitoring capability was included with a new telephone system for customer service operators. The monitoring system distributed incoming telephone calls from customers, timed the calls and allowed for supervisor eavesdropping on employee telephone conversations. This system was instituted under the guise of a work flow scheduling tool for determining the peak periods for telephone calls to determine when extra operators would be needed. Instead of using the monitoring system solely for that purpose, management also used the data to establish work performance standards, (seconds per transaction) and to bring disciplinary action against employees with “below average performance.” This electronic monitoring system introduced a pressure to perform above average because of fear of reprimand. Research has shown that such work pressure is not conducive to good performance but rather can bring about adverse health consequences (Cooper and Marshall 1976; Smith 1987). In fact, the monitoring system described was found to have increased employee stress and lowered the quality of production (Smith et al. 1992a).

Electronic monitoring can influence worker self-image and feelings of self-worth. In some cases, monitoring could enhance feelings of self-worth if the worker gets positive feedback. The fact that management has taken an interest in the worker as a valuable resource is another possible positive outcome. However, both effects may be perceived differently by workers, particularly if poor performance leads to punishment or reprimand. Fear of negative evaluation can produce anxiety and may damage self-esteem and self-image. Indeed electronic monitoring can create known adverse working conditions, such as paced work, lack of worker involvement, reduced task variety and task clarity, reduced peer social support, reduced supervisory support, fear of job loss, or routine work activities, and lack of control over tasks (Amick and Smith 1992; Carayon 1993).

Michael J. Smith

Positive aspects also exist since computers are able to do many of the simple, repetitive tasks that were previously done manually, which can reduce the repetitiveness of the job, increase the content of the job and make it more meaningful. This is not universally true, however, since many new computer jobs, such as data entry, are still repetitive and boring. Computers can also provide performance feedback that is not available with other technologies (Kalimo and Leppanen 1985), which can reduce ambiguity.

Some aspects of computerized work have been linked to decreased control, which has been identified as a major source of stress for clerical computer users. Uncertainty regarding the duration of computer-related problems, such as breakdown and slowdown, can be a source of stress (Johansson and Aronsson 1984; Carayon-Sainfort 1992). Computer-related problems can be particularly stressful if workers, such as airline reservation clerks, are highly dependent on the technology to perform their job.

Technology

The technology being used by the worker often defines his or her ability to accomplish tasks and the extent of physiological and psychological load. If the technology produces either too much or too little workload, increased stress and adverse physical health outcomes can occur (Smith et al. 1981; Johansson and Aronsson 1984; Ostberg and Nilsson 1985). Technology is changing at a rapid pace, forcing workers to adjust their skills and knowledge continuously to keep up. In addition, today’s skills can quickly become obsolete. Technological obsolescence may be due to job de-skilling and impoverished job content or to inadequate skills and training. Workers who do not have the time or resources to keep up with the technology may feel threatened by the technology and may worry about losing their job. Thus, workers’ fears of having inadequate skills to use the new technology are one of the main adverse influences of technology, which training, of course, can help to offset. Another effect of the introduction of technology is the fear of job loss due to increased efficiency of technology (Ostberg and Nilsson 1985; Smith, Carayon and Miezio 1987).

Intensive, repetitive, long sessions at the VDU can also contribute to increased ergonomic stress and strain (Stammerjohn, Smith and Cohen 1981; Sauter et al. 1983b; Smith et al. 1992b) and can create visual or musculoskeletal discomfort and disorders, as described elsewhere in the chapter.

Organizational factors

The organizational context of work can influence worker stress and health. When technology requires new skills, the way in which workers are introduced to the new technology and the organizational support they receive, such as appropriate training and time to acclimatize, has been related to the levels of stress and emotional disturbances experienced (Smith, Carayon and Miezio 1987). The opportunity for growth and promotion in a job (career development) is also related to stress (Smith et al. 1981). Job future uncertainty is a major source of stress for computer users (Sauter et al. 1983b; Carayon 1993a) and the possibility of job loss also creates stress (Smith et al. 1981; Kasl 1978).

Work scheduling, such as shift work and overtime, have been shown to have negative mental and physical health consequences (Monk and Tepas 1985; Breslow and Buell 1960). Shift work is increasingly used by companies that want or need to keep computers running continuously. Overtime is often needed to ensure that workers keep up with the workload, especially when work remains incomplete as a result of delays due to computer breakdown or misfunction.

Computers provide management with the capability to continuously monitor employee performance electronically, which has the potential to create stressful working conditions, such as by increasing work pressure (see the box “Electronic Monitoring”). Negative employee-supervisor relationships and feelings of lack of control can increase in electronically supervised workplaces.

The introduction of VDU technology has affected social relationships at work. Social isolation has been identified as a major source of stress for computer users (Lindström 1991; Yang and Carayon 1993) since the increased time spent working on computers reduces the time that workers have to socialize and receive or give social support. The need for supportive supervisors and co-workers has been well documented (House 1981). Social support can moderate the impact of other stressors on worker stress. Thus, support from colleagues, supervisor or computer staff becomes important for the worker who is experiencing computer-related problems but the computer work environment may, ironically, reduce the level of such social support available.

The individual

A number of personal factors such as personality, physical health status, skills and abilities, physical conditioning, prior experiences and learning, motives, goals and needs determine the physical and psychological effects just described (Levi 1972).

Improving the Psychosocial Characteristics of VDU Work

The first step in making VDU work less stressful is to identify work organization and job design features that can promote psychosocial problems so that they can be modified, always bearing in mind that VDU problems which can lead to job stress are seldom the result of single aspects of the organization or of job design, but rather, are a combination of many aspects of improper work design. Thus, solutions for reducing or eliminating job stress must be comprehensive and deal with many improper work design factors simultaneously. Solutions that focus on only one or two factors will not succeed. (See figure 2.)

Figure 2. Keys to reducing isolation and stress

Improvements in job design should start with the work organization providing a supportive environment for employees. Such an environment enhances employee motivation to work and feelings of security, and it reduces feelings of stress (House 1981). A policy statement that defines the importance of employees within an organization and is explicit on how the organization will provide a supportive environment is a good first step. One very effective means for providing support to employees is to provide supervisors and managers with specific training in methods for being supportive. Supportive supervisors can serve as buffers that “protect” employees from unnecessary organizational or technological stresses.

The content of job tasks has long been recognized as important for employee motivation and productivity (Herzberg 1974; Hackman and Oldham 1976). More recently the relationship between job content and job stress reactions has been elucidated (Cooper and Marshall 1976; Smith 1987). Three main aspects of job content that are of specific relevance to VDU work are task complexity, employee skills and career opportunities. In some respects, these are all related to the concept of developing the motivational climate for employee job satisfaction and psychological growth, which deals with the improvement of employees’ intellectual capabilities and skills, increased ego enhancement or self-image and increased social group recognition of individual achievement.

The primary means for enhancing job content is to increase the skill level for performing job tasks, which typically means enlarging the scope of job tasks, as well as enriching the elements of each specific task (Herzberg 1974). Enlarging the number of tasks increases the repertoire of skills needed for successful task performance, and also increases the number of employee decisions made while defining task sequences and activities. An increase in the skill level of the job content promotes employee self-image of personal worth and of value to the organization. It also enhances the positive image of the individual in his or her social work group within the organization.

Increasing the complexity of the tasks, which means increasing the amount of thinking and decision-making involved, is a logical next step that can be achieved by combining simple tasks into sets of related activities that have to be coordinated, or by adding mental tasks that require additional knowledge and computational skills. Specifically, when computerized technology is introduced, new tasks in general will have requirements that exceed the current knowledge and skills of the employees who are to perform them. Thus there is a need to train employees in the new aspects of the tasks so that they will have the skills to perform the tasks adequately. Such training has more than one benefit, since it not only may improve employee knowledge and skills, and thus enhance performance, but may also enhance employee self-esteem and confidence. Providing training also shows the employee that the employer is willing to invest in his or her skill enhancement, and thus promotes confidence in employment stability and job future.

The amount of control that an employee has over the job has a powerful psychosocial influence (Karasek et al. 1981; Sauter, Cooper and Hurrell 1989). Important aspects of control can be defined by the answers to the questions, “What, how and when?” The nature of the tasks to be undertaken, the need for coordination among employees, the methods to be used to carry out the tasks and the scheduling of the tasks can all be defined by answers to these questions. Control can be designed into jobs at the levels of the task, the work unit and the organization (Sainfort 1991; Gardell 1971). At the task level, the employee can be given autonomy in the methods and procedures used in completing the task.

At the work-unit level, groups of employees can self-manage several interrelated tasks and the group itself can decide on who will perform particular tasks, the scheduling of tasks, coordination of tasks and production standards to meet organizational goals. At the organization level, employees can participate in structured activities that provide input to management about employee opinions or quality improvement suggestions. When the levels of control available are limited, it is better to introduce autonomy at the task level and then work up the organizational structure, insofar as possible (Gardell 1971).

One natural result of computer automation appears to be an increased workload, since the purpose of the automation is to enhance the quantity and quality of work output. Many organizations believe that such an increase is necessary in order to pay for the investment in the automation. However, establishing the appropriate workload is problematic. Scientific methods have been developed by industrial engineers for determining appropriate work methods and workloads (the performance requirements of jobs). Such methods have been used successfully in manufacturing industries for decades, but have had little application in office settings, even after office computerization. The use of scientific means, such as those described by Kanawaty (1979) and Salvendy (1992), to establish workloads for VDU operators, should be a high priority for every organization, since such methods set reasonable production standards or work output requirements, help to protect employees from excessive workloads, as well as help to ensure the quality of products.

The demand that is associated with the high levels of concentration required for computerized tasks can diminish the amount of social interaction during work, leading to social isolation of employees. To counter this effect, opportunities for socialization for employees not engaged in computerized tasks, and for employees who are on rest breaks, should be provided. Non-computerized tasks which do not require extensive concentration could be organized in such a way that employees can work in close proximity to one another and thus have the opportunity to talk among themselves. Such socialization provides social support, which is known to be an essential modifying factor in reducing adverse mental health effects and physical disorders such as cardiovascular diseases (House 1981). Socialization naturally also reduces social isolation and thus promotes improved mental health.

Since poor ergonomic conditions can also lead to psychosocial problems for VDU users, proper ergonomic conditions are an essential element of complete job design. This is covered in some detail in other articles in this chapter and elsewhere in the Encyclopaedia.

Finding Balance

Since there are no “perfect” jobs or “perfect” workplaces free from all psychosocial and ergonomic stressors, we must often compromise when making improvements at the workplace. Redesigning processes generally involves “trade-offs” between excellent working conditions and the need to have acceptable productivity. This requires us to think about how to achieve the best “balance” between positive benefits for employee health and productivity. Unfortunately, since so many factors can produce adverse psychosocial conditions that lead to stress, and since these factors are interrelated, modifications in one factor may not be beneficial if concomitant changes are not made in other related factors. In general, two aspects of balance should be addressed: the balance of the total system and compensatory balance.

System balance is based on the idea that a workplace or process or job is more than the sum of the individual components of the system. The interplay among the various components produces results that are greater (or less) than the sum of the individual parts and determines the potential for the system to produce positive results. Thus, job improvements must take account of and accommodate the entire work system. If an organization concentrates solely on the technological component of the system, there will be an imbalance because personal and psychosocial factors will have been neglected. The model given in figure 1 of the work system can be used to identify and understand the relationships between job demands, job design factors, and stress which must be balanced.

Since it is seldom possible to eliminate all psychosocial factors that cause stress, either because of financial considerations, or because it is impossible to change inherent aspects of job tasks, compensatory balance techniques are employed. Compensatory balance seeks to reduce psychological stress by changing aspects of work that can be altered in a positive direction to compensate for those aspects that cannot be changed. Five elements of the work system—physical loads, work cycles, job content, control, and socialization—function in concert to provide the resources for achieving individual and organizational goals through compensatory balance. While we have described some of the potential negative attributes of these elements in terms of job stress, each also has positive aspects that can counteract the negative influences. For instance, inadequate skill to use new technology can be offset by employee training. Low job content that creates repetition and boredom can be balanced by an organizational supervisory structure that promotes employee involvement and control over tasks, and job enlargement that introduces task variety. The social conditions of VDU work could be improved by balancing the loads that are potentially stressful and by considering all of the work elements and their potential for promoting or reducing stress. The organizational structure itself could be adapted to accommodate enriched jobs in order to provide support to the individual. Increased staffing levels, increasing the levels of shared responsibilities or increasing the financial resources put toward worker well-being are other possible solutions.

Back

Introduction

The development of effective interfaces to computer systems is the fundamental objective of research on human-computer interactions.

An interface can be defined as the sum of the hardware and software components through which a system is operated and users informed of its status. The hardware components include data entry and pointing devices (e.g., keyboards, mice), information-presentation devices (e.g., screens, loudspeakers), and user manuals and documentation. The software components include menu commands, icons, windows, information feedback, navigation systems and messages and so on. An interface’s hardware and software components may be so closely linked as to be inseparable (e.g., function keys on keyboards). The interface includes everything the user perceives, understands and manipulates while interacting with the computer (Moran 1981). It is therefore a crucial determinant of the human-machine relation.

Research on interfaces aims at improving interface utility, accessibility, performance and safety, and usability. For these purposes, utility is defined with reference to the task to be performed. A useful system contains the necessary functions for the completion of tasks users are asked to perform (e.g., writing, drawing, calculations, programming). Accessibility is a measure of an interface’s ability to allow several categories of users—particularly individuals with handicaps, and those working in geographically isolated areas, in constant movement or having both hands occupied—to use the system to perform their activities. Performance, considered here from a human rather than a technical viewpoint, is a measure of the degree to which a system improves the efficiency with which users perform their work. This includes the effect of macros, menu short-cuts and intelligent software agents. The safety of a system is defined by the extent to which an interface allows users to perform their work free from the risk of human, equipment, data, or environmental accidents or losses. Finally, usability is defined as the ease with which a system is learned and used. By extension, it also includes system utility and performance, defined above.

Elements of Interface Design

Since the invention of shared-time operating systems in 1963, and especially since the arrival of the microcomputer in 1978, the development of human-computer interfaces has been explosive (see Gaines and Shaw 1986 for a history). The stimulus for this development has been essentially driven by three factors acting simultaneously:

First, the very rapid evolution of computer technology, a result of advances in electrical engineering, physics and computer science, has been a major determinant of user interface development. It has resulted in the appearance of computers of ever-increasing power and speed, with high memory capacities, high-resolution graphics screens, and more natural pointing devices allowing direct manipulation (e.g., mice, trackballs). These technologies were also responsible for the emergence of microcomputing. They were the basis for the character-based interfaces of the 1960s and 1970s, graphical interfaces of the late 1970s, and multi- and hyper-media interfaces appearing since the mid-1980s based on virtual environments or using a variety of alternate-input recognition technologies (e.g., voice-, handwriting-, and movement-detection). Considerable research and development has been conducted in recent years in these areas (Waterworth and Chignel 1989; Rheingold 1991). Concomitant with these advances was the development of more advanced software tools for interface design (e.g., windowing systems, graphical object libraries, prototyping systems) that greatly reduce the time required to develop interfaces.

Second, users of computer systems play a large role in the development of effective interfaces. There are three reasons for this. First, current users are not engineers or scientists, in contrast to users of the first computers. They therefore demand systems that can be easily learned and used. Second, the age, sex, language, culture, training, experience, skill, motivation and interest of individual users is quite varied. Interfaces must therefore be more flexible and better able to adapt to a range of needs and expectations. Finally, users are employed in a variety of economic sectors and perform a quite diverse spectrum of tasks. Interface developers must therefore constantly reassess the quality of their interfaces.

Lastly, intense market competition and increased safety expectations favour the development of better interfaces. These preoccupations are driven by two sets of partners: on the one hand, software producers who strive to reduce their costs while maintaining product distinctiveness that furthers their marketing goals, and on the other, users for whom the software is a means of offering competitive products and services to clients. For both groups, effective interfaces offer a number of advantages:

For software producers:

• better product image

• increased demand for products

• shorter training times

• lower after-sales service requirements

• solid base upon which to develop a product line

• reduction of the risk of errors and accidents

• reduction of documentation.

For users:

• shorter learning phase

• increased general applicability of skills

• improved use of the system

• increased autonomy using the system

• reduction of the time needed to execute a task

• reduction in the number of errors

• increased satisfaction.

Effective interfaces can significantly improve the health and productivity of users at the same time as they improve the quality and reduce the cost of their training. This, however, requires basing interface design and evaluation on ergonomic principles and practice standards, be they guidelines, corporate standards of major system manufacturers or international standards. Over the years, an impressive body of ergonomic principles and guidelines related to interface design has accumulated (Scapin 1986; Smith and Mosier 1986; Marshall, Nelson and Gardiner 1987; Brown 1988). This multidisciplinary corpus covers all aspects of character-mode and graphical interfaces, as well as interface evaluation criteria. Although its concrete application occasionally poses some problems—for example, imprecise terminology, inadequate information on usage conditions, inappropriate presentation—it remains a valuable resource for interface design and evaluation.

In addition, the major software manufacturers have developed their own guidelines and internal standards for interface design. These guidelines are available in the following documents:

• Apple Human Interface Guidelines (1987)

• Open Look (Sun 1990)

• OSF/Motif Style Guide (1990)

• IBM Common User Access guide to user interface design (1991)

• IBM Advanced Interface Design Reference (1991)

• The Windows interface: An application design guide (Microsoft 1992)

These guidelines attempt to simplify interface development by mandating a minimal level of uniformity and consistency between interfaces used on the same computer platform. They are precise, detailed, and quite comprehensive in several respects, and offer the additional advantages of being well-known, accessible and widely used. They are the de facto design standards used by developers, and are, for this reason, indispensable.

Furthermore, the International Organization for Standardization (ISO) standards are also very valuable sources of information about interface design and evaluation. These standards are primarily concerned with ensuring uniformity across interfaces, regardless of platforms and applications. They have been developed in collaboration with national standardization agencies, and after extensive discussion with researchers, developers and manufacturers. The main ISO interface design standard is ISO 9241, which describes ergonomic requirements for visual display units. It is comprised of 17 parts. For example, parts 14, 15, 16 and 17 discuss four types of human-computer dialogue—menus, command languages, direct manipulation, and forms. ISO standards should take priority over other design principles and guidelines. The following sections discuss the principles which should condition interface design.

A Design Philosophy Focused on the User

Gould and Lewis (1983) have proposed a design philosophy focused on the video display unit user. Its four principles are:

1. Immediate and continuous attention to users. Direct contact with users is maintained, in order to better understand their characteristics and tasks.
2. Integrated design. All aspects of usability (e.g., interface, manuals, help systems) are developed in parallel and placed under centralized control.
3. Immediate and continuous evaluation by users. Users test the interfaces or prototypes early on in the design phase, under simulated work conditions. Performance and reactions are measured quantitatively and qualitatively.
4. Iterative design. The system is modified on the basis of the results of the evaluation, and the evaluation cycle started again.

These principles are explained in further detail in Gould (1988). Very relevant when they were first published in 1985, fifteen years later they remain so, due to the inability to predict the effectiveness of interfaces in the absence of user testing. These principles constitute the heart of user-based development cycles proposed by several authors in recent years (Gould 1988; Mantei and Teorey 1989; Mayhew 1992; Nielsen 1992; Robert and Fiset 1992).

The rest of this article will analyse five stages in the development cycle that appear to determine the effectiveness of the final interface.

Task Analysis

Ergonomic task analysis is one of the pillars of interface design. Essentially, it is the process by which user responsibilities and activities are elucidated. This in turn allows interfaces compatible with the characteristics of users’ tasks to be designed. There are two facets to any given task:

1. The nominal task, corresponding to the organization’s formal definition of the task. This includes objectives, procedures, quality control, standards and tools.
2. The real task, corresponding to the users’ decisions and behaviours necessary for the execution of the nominal task.

The gap between nominal and real tasks is inevitable and results from the failure of nominal tasks to take into account variations and unforeseen circumstances in the work flow, and differences in users’ mental representations of their work. Analysis of the nominal task is insufficient for a full understanding of users’ activities.

Activity analysis examines elements such as work objectives, the type of operations performed, their temporal organization (sequential, parallel) and frequency, the operational modes relied upon, decisions, sources of difficulty, errors and recovery modes. This analysis reveals the different operations performed to accomplish the task (detection, searching, reading, comparing, evaluating, deciding, estimating, anticipating), the entities manipulated (e.g., in process control, temperature, pressure, flow-rate, volume) and the relation between operators and entities. The context in which the task is executed conditions these relations. These data are essential for the definition and organization of the future system’s features.

At its most basic, task analysis is composed of data collection, compilation and analysis. It may be performed before, during or after computerization of the task. In all cases, it provides essential guidelines for interface design and evaluation. Task analysis is always concerned with the real task, although it may also study future tasks through simulation or prototype testing. When performed prior to computerization, it studies “external tasks” (i.e., tasks external to the computer) performed with the existing work tools (Moran 1983). This type of analysis is useful even when computerization is expected to result in major modification of the task, since it elucidates the nature and logic of the task, work procedures, terminology, operators and tasks, work tools and sources of difficulty. In so doing, it provides the data necessary for task optimization and computerization.

Task analysis performed during task computerization focuses on “internal tasks”, as performed and represented by the computer system. System prototypes are used to collect data at this stage. The focus is on the same points examined in the previous stage, but from the point of view of the computerization process.

Following task computerization, task analysis also studies internal tasks, but analysis now focuses on the final computer system. This type of analysis is often performed to evaluate existing interfaces or as part of the design of new ones.

Hierarchical task analysis is a common method in cognitive ergonomics that has proven very useful in a wide variety of fields, including interface design (Shepherd 1989). It consists of the division of tasks (or main objectives) into sub-tasks, each of which can be further subdivided, until the required level of detail is attained. If data is collected directly from users (e.g., through interviews, vocalization), hierarchical division can provide a portrait of users’ mental mapping of a task. The results of the analysis can be represented by a tree diagram or table, each format having its advantages and disadvantages.

User Analysis

The other pillar of interface design is the analysis of user characteristics. The characteristics of interest may relate to user age, sex, language, culture, training, technical or computer-related knowledge, skills or motivation. Variations in these individual factors are responsible for differences within and between groups of users. One of the key tenets of interface design is therefore that there is no such thing as the average user. Instead, different groups of users should be identified and their characteristics understood. Representatives of each group should be encouraged to participate in the interface design and evaluation processes.

On the other hand, techniques from psychology, ergonomics and cognitive engineering can be used to reveal information on user characteristics related to perception, memory, cognitive mapping, decision-making and learning (Wickens 1992). It is clear that the only way to develop interfaces that are truly compatible with users is to take into account the effect of differences in these factors on user capacities, limits and ways of operating.

Ergonomic studies of interfaces have focused almost exclusively on users’ perceptual, cognitive and motor skills, rather than on affective, social or attitudinal factors, although work in the latter fields has become more popular in recent years. (For an integrated view of humans as information-processing systems see Rasmussen 1986; for a review of user-related factors to consider when designing interfaces see Thimbleby 1990 and Mayhew 1992). The following paragraphs review the four main user-related characteristics that should be taken into account during interface design.

Mental representation

The mental models users construct of the systems they use reflect the manner in which they receive and understand these systems. These models therefore vary as a function of users’ knowledge and experience (Hutchins 1989). In order to minimize the learning curve and facilitate system use, the conceptual model upon which a system is based should be similar to users’ mental representation of it. It should be recognized however that these two models are never identical. The mental model is characterized by the very fact that it is personal (Rich 1983), incomplete, variable from one part of the system to another, possibly in error on some points and in constant evolution. It plays a minor role in routine tasks but a major one in non-routine ones and during diagnosis of problems (Young 1981). In the latter cases, users will perform poorly in the absence of an adequate mental model. The challenge for interface designers is to design systems whose interaction with users will induce the latter to form mental models similar to the system’s conceptual model.

Learning

Analogy plays a large role in user learning (Rumelhart and Norman 1983). For this reason, the use of appropriate analogies or metaphors in the interface facilitates learning, by maximizing the transfer of knowledge from known situations or systems. Analogies and metaphors play a role in many parts of the interface, including the names of commands and menus, symbols, icons, codes (e.g., shape, colour) and messages. When pertinent, they greatly contribute to rendering interfaces natural and more transparent to users. On the other hand, when they are irrelevant, they can hinder users (Halasz and Moran 1982). To date, the two metaphors used in graphical interfaces are the desktop and, to a lesser extent, the room.

Users generally prefer to learn new software by using it immediately rather than by reading or taking a course—they prefer action-based learning in which they are cognitively active. This type of learning does, however, present a few problems for users (Carroll and Rosson 1988; Robert 1989). It demands an interface structure which is compatible, transparent, consistent, flexible, natural-appearing and fault tolerant, and a feature set which ensures usability, feedback, help systems, navigational aides and error handling (in this context, “errors” refer to actions that users wish to undo). Effective interfaces give users some autonomy during exploration.

Developing knowledge

User knowledge develops with increasing experience, but tends to plateau rapidly. This means that interfaces must be flexible and capable of responding simultaneously to the needs of users with different levels of knowledge. Ideally, they should also be context sensitive and provide personalized help. The EdCoach system, developed by Desmarais, Giroux and Larochelle (1993) is such an interface. Classification of users into beginner, intermediate and expert categories is inadequate for the purpose of interface design, since these definitions are too static and do not account for individual variations. Information technology capable of responding to the needs of different types of users is now available, albeit at the research, rather than commercial, level (Egan 1988). The current rage for performance-support systems suggests intense development of these systems in coming years.

Unavoidable errors

Finally, it should be recognized that users make mistakes when using systems, regardless of their skill level or the quality of the system. A recent German study by Broadbeck et al. (1993) revealed that at least 10% of the time spent by white-collar workers working on computers is related to error management. One of the causes of errors is users’ reliance on correction rather than prevention strategies (Reed 1982). Users prefer acting rapidly and incurring errors that they must subsequently correct, to working more slowly and avoiding errors. It is essential that these considerations be taken into account when designing human-computer interfaces. In addition, systems should be fault tolerant and should incorporate effective error management (Lewis and Norman 1986).

Needs Analysis

Needs analysis is an explicit part of Robert and Fiset’s development cycle (1992), it corresponds to Nielsen’s functional analysis and is integrated into other stages (task, user or needs analysis) described by other authors. It consists of the identification, analysis and organization of all the needs that the computer system can satisfy. Identification of features to be added to the system occurs during this process. Task and user analysis, presented above, should help define many of the needs, but may prove inadequate for the definition of new needs resulting from the introduction of new technologies or new regulations (e.g., safety). Needs analysis fills this void.

Needs analysis is performed in the same way as functional analysis of products. It requires the participation of a group of people interested by the product and possessing complementary training, occupations or work experience. This can include future users of the system, supervisors, domain experts and, as required, specialists in training, work organization and safety. Review of the scientific and technical literature in the relevant field of application may also be performed, in order to establish the current state of the art. Competitive systems used in similar or related fields can also be studied. The different needs identified by this analysis are then classified, weighted and presented in a format appropriate for use throughout the development cycle.

Prototyping

Prototyping is part of the development cycle of most interfaces and consists of the production of a preliminary paper or electronic model (or prototype) of the interface. Several books on the role of prototyping in human-computer interaction are available (Wilson and Rosenberg 1988; Hartson and Smith 1991; Preece et al. 1994).

Prototyping is almost indispensable because:

1. Users have difficulty evaluating interfaces on the basis of functional specifications—the description of the interface is too distant from the real interface, and evaluation too abstract. Prototypes are useful because they allow users to see and use the interface and directly evaluate its usefulness and usability.
2. It is practically impossible to construct an adequate interface on the first try. Interfaces must be tested by users and modified, often repeatedly. To overcome this problem, paper or interactive prototypes that can be tested, modified or rejected are produced and refined until a satisfactory version is obtained. This process is considerably less expensive than working on real interfaces.

From the point of view of the development team, prototyping has several advantages. Prototypes allow the integration and visualization of interface elements early on in the design cycle, rapid identification of detailed problems, production of a concrete and common object of discussion in the development team and during discussions with clients, and simple illustration of alternative solutions for the purposes of comparison and internal evaluation of the interface. The most important advantage is, however, the possibility of having users evaluate prototypes.

Inexpensive and very powerful software tools for the production of prototypes are commercially available for a variety of platforms, including microcomputers (e.g., Visual Basic and Visual C++ (™Microsoft Corp.), UIM/X (™Visual Edge Software), HyperCard (™Apple Computer), SVT (™SVT Soft Inc.)). Readily available and relatively easy to learn, they are becoming widespread among system developers and evaluators.

The integration of prototyping completely changed the interface development process. Given the rapidity and flexibility with which prototypes can be produced, developers now tend to reduce their initial analyses of task, users and needs, and compensate for these analytical deficiencies by adopting longer evaluation cycles. This assumes that usability testing will identify problems and that it is more economical to prolong evaluation than to spend time on preliminary analysis.

Evaluation of Interfaces

User evaluation of interfaces is an indispensable and effective way to improve interfaces’ usefulness and usability (Nielsen 1993). The interface is almost always evaluated in electronic form, although paper prototypes may also be tested. Evaluation is an iterative process and is part of the prototype evaluation-modification cycle which continues until the interface is judged acceptable. Several cycles of evaluation may be necessary. Evaluation may be performed in the workplace or in usability laboratories (see the special edition of Behaviour and Information Technology (1994) for a description of several usability laboratories).

Some interface evaluation methods do not involve users; they may be used as a complement to user evaluation (Karat 1988; Nielsen 1993; Nielsen and Mack 1994). A relatively common example of such methods consists of the use of criteria such as compatibility, consistency, visual clarity, explicit control, flexibility, mental workload, quality of feedback, quality of help and error handling systems. For a detailed definition of these criteria, see Bastien and Scapin (1993); they also form the basis of an ergonomic questionnaire on interfaces (Shneiderman 1987; Ravden and Johnson 1989).

Following evaluation, solutions must be found to problems that have been identified, modifications discussed and implemented, and decisions made concerning whether a new prototype is necessary.

Conclusion

This discussion of interface development has highlighted the major stakes and broad trends in the field of human-computer interaction. In summary, (a) task, user, and needs analysis play an essential role in understanding system requirements and, by extension, necessary interface features; and (b) prototyping and user evaluation are indispensable for the determination of interface usability. An impressive body of knowledge, composed of principles, guidelines and design standards, exists on human-computer interactions. Nevertheless, it is currently impossible to produce an adequate interface on the first try. This constitutes a major challenge for the coming years. More explicit, direct and formal links must be established between analysis (task, users, needs, context) and interface design. Means must also be developed to apply current ergonomic knowledge more directly and more simply to the design of interfaces.

Back

Introduction

Ergonomics standards can take many forms, such as regulations which are promulgated on a national level, or guidelines and standards instituted by international organizations. They play an important role in improving the usability of systems. Design and performance standards give managers confidence that the systems they buy will be capable of being used productively, efficiently, safely and comfortably. They also provide users with a benchmark by which to judge their own working conditions. In this article we focus on the International Organization for Standardization (ISO) ergonomics standard 9241 (ISO 1992) because it provides important, internationally recognized, criteria for selecting or designing VDU equipment and systems. ISO carries out its work through a series of technical committees, one of which is ISO TC 159 SC4 Ergonomics of Human System Interaction Committee, which is responsible for ergonomics standards for situations in which human beings and technological systems interact. Its members are representatives of the national standards bodies of member countries and meetings involve national delegations in discussing and voting on resolutions and technical documents. The primary technical work of the committee takes place in eight Working Groups (WGs), each of which has responsibility for different work items listed in figure 1. This sub-committee has developed ISO 9241.

Figure 1. Technical Working Groups of the Ergonomics of Human System Interaction Technical Committee (ISO TC 159 SC4). ISO 9241: Five working groups broke down the “parts” of the standard to those listed below. This illustration shows the correspondence between the parts of the standard and the various aspects of the workstation with which they are concerned

 The work of the ISO has major international importance. Leading manufacturers pay great heed to ISO specifications. Most producers of VDUs are international corporations. It is obvious that the best and most effective solutions to workplace design problems from the international manufacturers’ point of view should be agreed upon internationally. Many regional authorities, such as the European Standardization Organization (CEN) have adopted ISO standards wherever appropriate. The Vienna Agreement, signed by the ISO and CEN, is the official instrument which ensures effective collaboration between the two organizations. As different parts of ISO 9241 are approved and published as international standards, they are adopted as European standards and become part of EN 29241. Since CEN standards replace national standards in the European Union (EU) and the European Free Trade Agreement (EFTA) Member States, the significance of ISO standards in Europe has grown, and, in turn, has also increased pressure on the ISO to efficiently produce standards and guidelines for VDUs.

User performance standards

An alternative to product standards is to develop user performance standards. Thus, rather than specify a product feature such as character height which it is believed will result in a legible display, standards makers develop procedures for testing directly such characteristics as legibility. The standard is then stated in terms of the user performance required from the equipment and not in terms of how that is achieved. The performance measure is a composite including speed and accuracy and the avoidance of discomfort.

User performance standards have a number of advantages; they are

• relevant to the real problems experienced by users

• tolerant of developments in the technology

• flexible enough to cope with interactions between factors.

However, user performance standards can also suffer a number of disadvantages. They cannot be totally complete and scientifically valid in all cases, but do represent reasonable compromises, which require significant time to obtain the agreement of all the parties involved in standards-setting.

Coverage and Use of ISO 9241

The VDU ergonomics requirements standard, ISO 9241, provides detail on ergonomic aspects of products, and on assessing the ergonomic properties of a system. All references to ISO 9241 also apply to EN 29241. Some parts provide general guidance to be considered in the design of equipment, software and tasks. Other parts include more specific design guidance and requirements relevant to current technology, since such guidance is useful to designers. In addition to product specifications, ISO 9241 emphasizes the need to specify factors affecting user performance, including how to assess user performance in order to judge whether or not a system is appropriate to the context in which it will be used.

ISO 9241 has been developed with office-based tasks and environments in mind. This means that in other specialized environments some acceptable deviation from the standard may be needed. In many cases, this adaptation of the office standard will achieve a more satisfactory result than the “blind” specification or testing of an isolated standard specific to a given situation. Indeed, one of the problems with VDU ergonomics standards is that the technology is developing faster than standards makers can work. Thus it is quite possible that a new device may fail to meet the strict requirements in an existing standard because it approaches the need in question in a way radically different from any that were foreseen when the original standard was written. For example, early standards for character quality on a display assumed a simple dot matrix construction. Newer more legible fonts would have failed to meet the original requirement because they would not have the specified number of dots separating them, a notion inconsistent with their design.

Unless standards are specified in terms of the performance to be achieved, the users of ergonomics standards must allow suppliers to meet the requirement by demonstrating that their solution provides equivalent or superior performance to achieve the same objective.

The use of the ISO 9241 standard in the specification and procurement process places display screen ergonomics issues firmly on management’s agenda and helps to ensure proper consideration of these issues by both procurer and supplier. The standard is therefore a useful part of the responsible employer’s strategy for protecting the health, safety and productivity of display screen users.

General issues

ISO 9241 Part 1 General introduction explains the principles underlying the multipart standard. It describes the user performance approach and provides guidance on how to use the standard and on how conformance to parts of ISO 9241 should be reported.

ISO 9241 Part 2 Guidance on task requirements provides guidance on job and task design for those responsible for planning VDU work in order to enhance the efficiency and the well-being of individual users by applying practical ergonomic knowledge to the design of office VDU tasks. Objectives and characteristics of task design are also discussed (see figure 2) and the standard describes how task requirements may be identified and specified within individual organizations and can be incorporated into the organization’s system design and implementation process.

Figure 2. Guidance and task requirements

Case Study: Display Screen Equipment Directive (90/270/EEC)

The Display Screen Directive is one in a series of “daughter”directives dealing with specific aspects of health and safety. The directives form part of the European Union’s programme for promoting health and safety in the single market. The “parent” or “Framework” Directive (89/391/EEC) sets out the general principles of the Community’s approach to Health and Safety. These common principles include the avoidance of risk, where possible, by eliminating the source of the risk and the encouragement of collective protective measures instead of individual protective measures.

Where risk is unavoidable, it must be properly evaluated by people with the relevant skills and measures must be taken which are appropriate to the extent of the risk. Thus if the assessment shows that the level of risk is slight, informal measures may be entirely adequate. However, where significant risk is identified, then stringent measures must be taken. The Directive itself only placed obligations on Member States of the EU, not on individual employers or manufacturers. The Directive required Member States to transpose the obligations into appropriate national laws, regulations and administrative provisions. These in turn place obligations on employers to ensure a minimum level of health and safety for display screen users.

Hardware and environmental ergonomics issues

Display screen

ISO 9241 (EN 29241) Part 3 Visual display requirements specifies the ergonomic requirements for display screens which ensure that they can be read comfortably, safely and efficiently to perform office tasks. Although it deals specifically with displays used in offices, the guidance is appropriate to specify for most applications which require general purpose displays. A user performance test which, once approved, can serve as the basis for performance testing and will become an alternate route to compliance for VDUs.

ISO 9241 Part 7 Display requirements with reflections. The purpose of this part is to specify methods of measurement of glare and reflections from the surface of display screens, including those with surface treatments. It is aimed at display manufacturers who wish to ensure that anti-reflection treatments do not detract from image quality.

ISO 9241 Part 8 Requirements for displayed colours. The purpose of this part is to deal with the requirements for multicolour displays which are largely in addition to the monochrome requirements in Part 3, requirements for visual display in general.

Keyboard and other input devices

ISO 9241 Part 4 Keyboard requirements requires that the keyboard should be tiltable, separate from the display and easy to use without causing fatigue in the arms or hands. This standard also specifies the ergonomic design characteristics of an alphanumeric keyboard which may be used comfortably, safely and efficiently to perform office tasks. Again, although Part 4 is a standard to be used for office tasks, it is appropriate to most applications which require general purpose alphanumeric keyboards. Design specifications and an alternative performance test method of compliance are included.

ISO 9241 Part 9 Requirements for non-keyboard input devices specifies the ergonomic requirements from such devices as the mouse and other pointing devices which may be used in conjunction with a visual display unit. It also includes a performance test.

Workstations

ISO 9241 Part 5 Workstation layout and postural requirements facilitates efficient operation of the VDU and encourages the user to adopt a comfortable and healthy working posture. The requirements for a healthy, comfortable posture are discussed. These include:

• the location of frequently used equipment controls, displays and work surfaces within easy reach

• the opportunity to change position frequently

• the avoidance of excessive, frequent and repetitive movements with extreme extension or rotation of the limbs or trunk

• support for the back allowing an angle of 90 degrees to 110 degrees between back and thighs.

The characteristics of the workplace which promote a healthy and comfortable posture are identified and design guidelines given.

Working environments

ISO 9241 Part 6 Environmental requirements specifies the ergonomic requirements for the visual display unit working environment which will provide the user with comfortable, safe and productive working conditions. It covers the visual, acoustic and thermal environments. The objective is to provide a working environment which should facilitate efficient operation of the VDU and provide the user with comfortable working conditions.

The characteristics of the working environment which influence efficient operation and user comfort are identified, and design guidelines presented. Even when it is possible to control the working environment within strict limits, individuals will differ in their judgements of its acceptability, partly because individuals vary in their preferences and partly because different tasks may require quite different environments. For example, users who sit at VDUs for prolonged periods are far more sensitive to draughts than users whose work involves moving about an office and only working at the VDU intermittently.

VDU work often restricts the opportunities that individuals have for moving about in an office and so some individual control over the environment is highly desirable. Care must be taken in common work areas to protect the majority of users from extreme environments which may be preferred by some individuals.

Software ergonomics and dialogue design

ISO 9241 Part 10 Dialogue principles presents ergonomic principles which apply to the design of dialogues between humans and information systems, as follows:

• suitability for the task

• self-descriptiveness

• controllability

• conformity with user expectations

• error tolerance

• suitability for individualization

• suitability for learning.

The principles are supported by a number of scenarios which indicate the relative priorities and importance of the different principles in practical applications. The starting point for this work was the German DIN 66234 Part 8 Principles of Ergonomic Dialogue Design for Workplaces with Visual Display Units.

ISO 9241 Part 11 Guidance on usability specification and measures helps those involved in specifying or measuring usability by providing a consistent and agreed framework of the key issues and parameters involved. This framework can be used as part of an ergonomic requirements specification and it includes descriptions of the context of use, the evaluation procedures to be carried out and the criterion measures to be satisfied when the usability of the system is to be evaluated.

ISO 9241 Part 12 Presentation of information provides guidance on the specific ergonomics issues involved in representing and presenting information in a visual form. It includes guidance on ways of representing complex information, screen layout and design and the use of windows. It is a useful summary of the relevant materials available among the substantial body of guidelines and recommendations which already exist. The information is presented as guidelines without any need for formal conformance testing.

ISO 9241 Part 13 User guidance provides manufacturers with, in effect, guidelines on how to provide guidelines to users. These include documentation, help screens, error handling systems and other aids that are found in many software systems. In assessing the usability of a product in practice, real users should take into account the documentation and guidance provided by the supplier in the form of manuals, training and so on, as well as the specific characteristics of the product itself.

ISO 9241 Part 14 Menu dialogues provides guidance on the design of menu-based systems. It applies to text-based menus as well as to pull-down or pop-up menus in graphical systems. The standard contains a large number of guidelines developed from the published literature and from other relevant research. In order to deal with the extreme variety and complexity of menu-based systems, the standard employs a form of “conditional compliance”. For each guideline, there are criteria to help establish whether or not it is applicable to the system in question. If it is determined that the guidelines are applicable, criteria to establish whether or not the system meets those requirements are provided.

ISO 9241 Part 15 Command dialogues provides guidance for the design of text-based command dialogues. Dialogues are the familiar boxes which come onto the screen and query the VDU user, such as in a search command. The software creates a “dialogue” in which the user must supply the term to be found, and any other relevant specifications about the term, such as its case or format.

ISO 9241 Part 16 Direct manipulation dialogues deals with the design of direct manipulation dialogues and WYSIWYG (What You See Is What You Get) dialogue techniques, whether provided as the sole means of dialogue or combined with some other dialogue technique. It is envisaged that the conditional compliance developed for Part 14 may be appropriate for this mode of interaction also.

ISO 9241 Part 17 Form-filling dialogues is in the very early stages of development.

Back