ON THE CONCEPT OF ISO 9241-SERIES
ISO 9241 "Ergonomic requirements for office work with visual display terminal (VDTs)" is a series of 17 standards which deals with various aspects of working with computers including task requirements, work environment- and hard- and software-related requirements. The subjects which are closely related to the workplace and the work environment were planned to be treated by the same working group in order to be able to deal with interdependencies between them. For example, using a mouse or a tablet requires additional work surface and thus, may result in an increased demand for workspace. Another example is using two different input devices (e.g. keyboard and mouse) within the same context which requires an optimization which is not needed if each device is used alone.
The overall concept of ISO 9241 is explained in the paper on workplace and work environment. For the description of the treatment of the input devices, the concept of usability is extremely important. In its part 11, ISO 9241 defines the concept of usability which qualifies it as a quality concept: The components of usability are effectiveness, efficiency and satisfaction. Effectiveness is defined as the accuracy and completeness with which users achieve specified goals. Efficiency represents the resources expended in relation to the accuracy and completeness with which users achieve goals. Both, efficiency and effectiveness, are components of user performance whereas satisfaction is defined as the comfort and acceptability of use. The context of use consists of descriptions of the users, goals, tasks, equipment (hardware, software and materials), and the physical and social environments in which a product is used. A product has no intrinsic usability, but one under a specified context of use.
Following this concept, any means enabling a user to introduce the intended data in the intended form would be acceptable from an ergonomic point of view regardless of its technical features if a required level of effectiveness and efficiency is given and the satisfaction with the use of the tool is sufficient. Originally, it was intended to standardize the "performance" and not to include any technical attributes in ISO 9241. During the later stages of the work it became apparent that this approach was not easy to understand - and also not easy to formulate.
For the reason given above, the working group responsible for the work, WG3, has developed a rather technical standard on keyboards, ISO 9241-4, which deviates from other standards only by providing an alternative test method for new designs. This seems acceptable since the knowledge on keyboards is very old and the usage of them is very conservative.
For all other input devices, a standard with an unfamiliar name "Non-keyboard input devices", ISO 9241-9, was created. Although this standard specifies technical attributes to a certain extent the main focus of it is enabling the development and the use of any technical means as an input device when it "fits the purpose". Since it is not easy to specify how this purpose should be determined, a number of the so-called "task-primitives" were defined which allow to measure the "performance" of the device, i.e. the level of efficiency, effectiveness and satisfaction. The decision whether a given device is usable for a given task can be taken by considering the decisive task primitive for that task.
ISO 9241-4: KEYBOARD REQUIREMENTS Purpose and scope This part of ISO 9241 applies to linear detachable keyboards designed for stationary use. It gives guidance on the design of keyboards used for typical office tasks so that the limitations and capabilities of users are considered. It gives guidance based on ergonomic factors for keyboard layout arrangements, the physical characteristics of the individual keys and the overall design of the housing containing the keys.
It may sound surprising for many ergonomists that the subject of the standard is a linear keyboard which is believed to cause various significant problems. However, even for those convinced of the benefits of alternative designs gradual improvements for conventional keyboards seem rewarding.
Guiding principles
ISO 9241-4 states "When selecting design criteria for a keyboard for a specified task, the relevant considerations are based on the functionality to be offered by the keyboard and by other input devices. These considerations can suggest selecting the minimum possible size of the keyboard determined by the number and the adequate grouping of the keys" In addition, it is stated "The objective of an ergonomic design is to ensure that the keyboard allows the user to locate and operate the appropriate keys accurately, quickly and without discomfort." The standard also refers to the - forgotten - link with user training "In addition, adequate training of the user can contribute substantially to all objectives (efficiency, effectiveness and satisfaction)."
Whether or not these guiding principles are met can be checked by the degree a product meets the "performance criterion" of the standard, i.e., "that the keyboard is usable for its designated purpose. It is considered usable if users can achieve a satisfactory level of keying performance on a given task and maintain a satisfactory level of effort and comfort."
Design requirements and recommendations
The standard includes a number of design requirements which add a significant number of ergonomic criteria to this normative document than has ever existed in standardization of keyboards. This was necessary because of the ubiquitous negligence concerning the importance of the keyboard for the last two decades as a result of the optimistic hope voice input or something else would make it obsolete. In the year 2000, the dreams of Marconi who had this idea first in 1909 did not come true. Thus, the standard states "The keyboard is currently the principal input device used by operators to enter information into interactive office computer systems."
The design requirements and recommendations include
* General design of the keyboard (e.g. palm rests, height, slope and slope adjustment, material properties)
* Design of keys (e.g. key layout and centre line spacing, key-- top design, key displacement and force, keying feedback, key roll-over, durability of legends etc.)
Alternative test route
The alternative test route does not belong to the normative provisions of ISO 9241-4 because some individuals who were in favor of flexible standards - or even had initiated the type of approach which had lead to ISO 9241 - have decided not to support such ideas any more. Whatever the real reason may be, it seems to lie outside the boundaries of ergonomics. The real reasons are likely to be traced in the history of US-litigation on keyboards and RSI resp. CTD. This history inhibits any claims of companies with older products that a new product is more "usable" if usability has any connection to safety and health. Since "ergonomics" can never be isolated from safety and/or health the problem will remain in the foreseeable future. However, in most countries, general legal conventions will allow to apply the alternative test route without any change in the wording of the standard.
This test route shows how a novel design can be tested anc introduced as an equivalent for a conventional design. Possibly this is an introduction of a new convention.
The fear that some vendors could use such methods as a loo hole to avoid some restrictions of existing standards is not justifled since tests of the required kind are not quick and dirty and anyone who applies them must be fully aware of the much easier "non-alternative-compliance route".
Summary and conclusion
ISO 92414 is in general a conventional technical standard which introduces a significant number of ergonomic provision: never considered in standardization before. It falls short of introducing the general approach that any input device which meet the usability goals may be considered as "ergonomically acceptable". However, the nature of the object as a well-known device for about 150 years may help to understand the outcome of the standardization work.
This standard does not answer the question whether non-linear keyboard layouts are more beneficial for the users. Dealing with alternatives in a standard is not necessary if the "standards solution does not inhibit novel solutions. This is the case with IS, 9241-4.
The really important ergonomic problem of users is not caused by the keyboard layout alone but by its simultaneous or concurrent use at the same workplace with other input devices, i most cases with a mouse. Today, almost all new equipment is delivered with keyboards with three sections according to ISO/lE, 9995 (alphanumeric, editing and numeric sections) adding to a width of the key fields of 450 mm. This width exceeds the shoulder breadth of 100% adult female and more than 95% adult ma: users regardless of their origin. Thus, any adult user needs to e. tend her or his right shoulder to a certain degree to be able to use a mouse (see fig. 1). Children work in a more awkward posture
Users who need good access to the alphanumeric part of the keyboard and to the mouse cannot maintain a neutral posture of their right arm. Their posture is determined by the location of the alphanumeric section which is placed to the left side of the keyboard. The distance between the middle of this section and the closest point where a mouse can be placed is about 350 mm! This is about 150 mm beyond the right shoulder of the 50th percentile adult male user (DIN 33402-2) and about 200 mm of the 5th percentile female user.
These figures show that the main ergonomic problem of the keyboard is not the keyboard itself. The contribution of the keyboard to the problem is that parts of it many people never use (editing and numeric sections) occupy the most important space in the environment, i.e. the space under the right hand of the user, while using the keyboard for its original purpose.
Fig. 1: (not shown)
ISO 9241-9: REQUIREMENTS FOR NON-KEYBOARD INPUT DEVICES
Purpose and scope
This part of ISO 9241 applies to several types of non-keyboard input devices designed for stationary use. It gives guidance based on ergonomic factors for the following input devices: mice, pucks, joysticks, trackballs, tablets and overlays, touch sensitive screens, styli, and light pens. It gives guidance on the design of these devices used for typical office tasks so that the limitations and capabilities of users are considered. This part of ISO 9241 specifies methods for determining conformance through observation and by measuring the physical attributes of the various devices.
Guiding principles of ISO 9241-9
The standard introduces four main guiding principles: Appropriateness, operability, controllability and (optimum) biomechanical load. The main principle operability is formed by eight principles (obviousness, predictability, consistency, compatibility, efficiency, effectiveness and feedback). Controllability is formed by five principles (responsiveness, interference, grip surface, device access and control access).
Due to the fact that ISO regulations require a measurement method for each requirement in a standard, the principles have been worded in a somewhat misleading way. For example, compatibility is worded as: "An input device is user compatible when its design accommodates the intended user cognitive and anthropometric characteristics and biomechanical capabilities." instead of "Input devices shall be user compatible. This is achieved when the design accommodates the intended user cognitive and anthropometric characteristics and biomechanical capabilities."
Establishing a sufficient number of measurement methods for all input devices and all user populations with different cognitive and anthropometric characteristics and biomechanical capabilities would be a compelling job for a research lab for the whole decade, but it would be one of many the standardization group needs to solve just for the principles. On the other hand, a standardization group is given only three years for developing a standard from scratch whereas the wheels of the ISO bureaucracy need up to 18 months to publish a completed manuscript. This is the reason why the WG3 was not able to formulate clear requirements.1. However, the designer of a new product should read all principles as requirements. Successfully applying them may be decisive for the overall performance of the product in the market. Nature of the guidance
The guidance given by ISO 9241-9 is fourfold:
* Guiding principles for all input devices as ultimate design goals
* Design requirements and recommendations for all input devices (e.g. resolution, repositioning, consideration of handedness)
* Design requirements and recommendations for specific input devices (mice, pucks, joysticks, trackballs, tablets and overlays, styli and lightpens, touch sensitive screens)
* Definitions of and measurement methods for task primitives
The definition of task primitives, i.e. fundamental actions (pointing, selecting, dragging, tracing, free-hand-input) associated with using a non-keyboard input device, is a unique feature of this standard. While designing or evaluating an input device the relevant task primitive can be used to characterize the performance of a certain device. For example, one can use them to select the appropriate size of a graphic tablet for different tasks and screen sizes.
ISO 9241-9 specifies a number of measurement and evaluation methods for usability testing, e.g. tapping or dragging tests for measuring effectiveness and efficiency or questionnaires for the assessment of user satisfaction. All methods are described in informative annexes. The annexes are intended to help designers, manufacturers, and system integrators assess the usability and ergonomic aspects of current and newly designed input devices. The assessment methodologies may also be used by organizations who need to determine whether a particular input device meets usability requirements.
In some respect, the guidance given cannot cover all relevant aspects concerning the usability of a type of a device. For example, no hand-held device can draw a straight line without additional help, but with adequate help any device can be used even by a blind person to accomplish this task. This is indicated by a note in the standard "Input device appropriateness may be enhanced by software." Some information the user needs for the correct operation of the device is not generated by it but by the system. In this case, one can only require what the device can perform at all. This is, for example, the case for the signal speed which is relevant for the visual feedback by mice. To properly operate a mouse, the result of the movement must be visible within 20 ms. The corresponding statement in the standard reads: "The feed forward signal from the input device to the system should occur within 20 ms." The standard cannot require that the visual feedback should occur within the acceptable time period because an input device generally does not give visual feedback.
Summary and conclusion
ISO 9241-9 is a new type of standard which regulates a variety of different products which may be used or even need to be used as a replacement of another (e.g. tablet instead of mouse and vice versa). The difficulties stemming from this background are aggravated by the input devices being normally used together with a keyboard, this means with a rather bulky device. Such difficulties and the possible substantial impact of the software on the usability of input devices had to be taken into account while developing this standard. The structure of the standard also reflects the attempt not to inhibit novel designs by fixing features of the existing.
Applying this part of ISO 9241 means that two levels of design requirements and recommendations (general requirements for all devices, dedicated requirements for the specific device) need to be considered together with the guiding principles of the standard which form an important set of requirements without being worded as such.
ISO 9241-9 is planned as a major step towards materializing the usability concept. It gives guidance for those who want to spend some effort in improving input devices and provides tools to evaluate the (hopefully successful) results.
OUTLOOK
ISO 9241-9 is a standard with a subject which is partly older than computer usage in offices, joysticks have existed before computers, and partly in rapid change (e.g. voice or gesture input). Some input devices have been very successful from the beginning, e.g. the mouse, while others like voice input still need substantial steps forward to become an everyday tool. Surprisingly, the voice input has the longest history of them: In the year 1909 Marconi had announced a device which would enable a speaker to type a perfect business letter by speaking into it. The world of the year 2000 knows few computer programs which may be able to convert 95% of spoken words into type. It is not unlikely that 99% could be reached not far from 2009. Even then, the perfect business letter generated from spoken words may still need a secretary. This is one of the reasons why voice input as well as some other novel input means are not included in the scope of ISO 9241-9.
In the year 2009, the input device Marconi tried to get rid of a century ago, the keyboard, is likely to remain an important input device. A good reason to develop new input devices which fit better with the keyboard and keyboards for concurrent use with other input devices.
ISO 9241-4 is not the only international standard which describes keyboards. It refers to ISO/IEC 9995 with existing eight parts in which, for example, the layout and the sections of the keyboard are described. While the distribution of responsibilities between two standardization groups dealing with the same subject was somewhat tolerable in this case, the purely ergonomic issue of split keyboards was standardized outside of the responsibility of the ISO technical committee ISO/TC 159 Ergonomics (ISO/ IEC 15411). The ongoing efforts to establish new ergonomic or ergonomic related standards parallel to those of the responsible technical committee which is not limited to the project named here provide us with some excellent food for thought, e.g. whether or not to recommend ISO applying some kind of quality control resp. quality assurance measures by using the excellent advice given in ISO 9000 series. For the time being, speaking of confusion with respect to some projects is not overexaggerated.
Each standard is being reviewed every five years. Thus in the year 2005, it will become necessary to evaluate the experiences of designers and test agencies with the standard ISO 9241-9 and its methods. Everyone should feel encouraged to report her or his experience.
Footnote
1. The completion of this work took substantially longer time, however, this was due to other circumstances.
References
LITERATURE
References
ISO 9241-4 Ergonomic requirements for office work with visual display terminals (VDTs), Keyboard requirements
ISO 9241-9 Ergonomic requirements for office work with visual display terminals (VDTs), Requirements for non-keyboard input devices
ISO 9241-11 Ergonomic requirements for office work with visual display terminals (VDTs), Guidance on usability
DIN ISO/IEC 9995, Information technology - Keyboard layouts for text and office systems
ISO/IEC 15411, Information Processing - Segmented Keyboard Layouts
AuthorAffiliation
Ahmet E. Cakir
ERGONOMIC Institute
Berlin, Germany
Copyright Human Factors and Ergonomics Society 2000
