Guidance on Usability standards

Standards related to human-centred design fall into two categories:

process-oriented: these specify procedures and processes to be followed.
product-oriented: these specify required attributes of the user interface.

Some product oriented standards specify the requirements in terms of performance rather than product attributes. These standards describe the users, tasks,
and context of use and assess usability in terms of user performance and satisfaction to be achieved.

Process oriented standards

ISO 6385 : 1981, Ergonomic principles in the design of work systems
ISO 6385 sets out the ergonomic principles which should be applied to the design of work systems. ISO 13407 is based on these principles and the description of the aims and objectives of ergonomics which are contained in ISO 6385.

ISO/DIS 13407 (1997) Human-centred design processes for interactive systems
This standard provides guidance on human-centred design activities throughout the life cycle of interactive computer-based systems. It is a tool for those managing design processes and provides guidance on sources of information and standards relevant to the human-centred approach. It describes
human-centred design as a multi-disciplinary activity, which incorporates human factors and ergonomics knowledge and techniques with the objective of enhancing effectiveness and efficiency, improving human working conditions, and counteracting possible adverse effects of use on human health, safety and performance.

ISO 9241-1: 1993 Ergonomic requirements for office work with visual display terminals (VDTs) - General Introduction
This part introduces the multi-part standard ISO 9241 for the ergonomic requirements for the use of visual display terminals for office tasks and explains some of the basic underlying principles. It provides some guidance on how to use the standard and describes how conformance to parts of ISO 9241 should be reported.

ISO 9241-2 : 1993 : Guidance on task requirements
This part deals with the design of tasks and jobs involving work with visual display terminals. It provides guidance on how task requirements may be identified
and specified within individual organizations and how task requirements can be incorporated into the system design and implementation process.

ISO /DIS 9241-11 : Guidance on Usability
This part provides the definition of usability which is used in ISO 13407.
Usability: the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.

ISO/DIS 9241-11 explains how to identify the information which it is necessary to take into account when specifying or evaluating usability in terms of measures of user performance and satisfaction. Guidance is given on how to describe the context of use of the product (hardware, software or service) and the required measures of usability in an explicit way. It includes an explanation of how the usability of a product can be specified and evaluated as part of a quality system, for example one which conforms to ISO 9001. It also explains how measures of user performance and satisfaction can be used to measure how any component of a work system affects the quality of the
whole work system in use.

ISO 10075-1 : 1994 Ergonomic principles related to mental work-load - General terms and definitions.
This part of ISO 10075 explains the terminology and provides definitions in the area of mental workload.

ISO/IEC CD 14598-1 :Information Technology - Evaluation of Software Products - General guide
The concept of quality in use has been used in ISO/IEC 14598-1 to distinguish between quality as an inherent characteristic of a software product and the quality which is achieved when a software product is used under stated conditions, that is, a specified context of use. This definition of quality in use is very similar to the definition of usability in ISO/DIS 9241-11. The use of the term quality in use therefore implies that it is necessary to take account of human-centred issues in evaluating software products.

Quality in use: the extent to which an entity satisfies stated and implied needs when used under stated conditions
Standards of this type can be used to support the following activities:
:: specification of overall quality and usability requirements and evaluation against these requirements (ISO/DIS 9241-11 and ISO/IEC CD 14598-1).
:: incorporation of usability into a quality system (ISO/DIS 9241-11).
:: guiding the process of user-centred design (ISO/DIS 13407).

Product oriented standards
In the product-oriented view, usability is seen as one relatively independent contribution to software quality, and is defined in this way in ISO/IEC 9126 :1991 : Information technology, Software product evaluation - Quality characteristics and guidelines for their use:

Œa set of attributes of software which bear on the effort needed for use and on the individual assessment of such use by a stated or implied set of users¹.

Usable products can be designed by incorporating product features and attributes known to benefit users in particular contexts of use. ISO 9241 provides requirements and recommendations relating to the attributes of the hardware, software and environment which contribute to usability, and the ergonomic
principles underlying them. Parts 3 to 9 contain hardware design requirements and guidance which can have implications for software. Parts 10 to 17 of ISO 9241 and other standards deal specifically with attributes of the software:

ISO 9241-3: 1993 Visual display requirements
This part specifies the ergonomics 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, it is appropriate to specify it for most applications which require general purpose displays to
be used in an office-like environment.

ISO DIS 9241-4 Keyboard requirements
This part specifies the ergonomics design characteristics of an alphanumeric keyboard which may be used comfortably, safely and efficiently to perform office
tasks. Keyboard layouts are dealt with separately in various parts of ISO/IEC 9995: 1994 Information Processing - Keyboard Layouts for Text and Office
Systems

ISO DIS 9241-5 Workstation layout and postural requirements
This part specifies the ergonomics requirements for a Visual Display Terminal workplace which will allow the user to adopt a comfortable and efficient
posture.

ISO DIS 9241-6 Environmental requirements
This part specifies the ergonomics requirements for the Visual Display Terminal working environment which will provide the user with comfortable, safe and
productive working conditions.

ISO DIS 9241-7 Display requirements with reflections
This part specifies 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 DIS 9241-8 Requirements for displayed colours
This part specifies the requirements for multi-colour displays which are largely in addition to the monochrome requirements in Part 3.

ISO DIS 9241-9 Requirements for non-keyboard input devices
This part specifies the ergonomics requirements for non-keyboard input devices which may be used in conjunction with a visual display terminal. It covers such devices as the mouse, trackerball and other pointing devices. It also includes a performance test. It does not address voice input.

ISO 9241-10: 1996 Dialogue principles
This part deals with general ergonomic principles which apply to the design of dialogues between humans and information systems: suitability for the task, suitability for learning, suitability for individualisation, conformity with user expectations, self descriptiveness, controllability, and error tolerance.

ISO/CD 9241-12: Presentation of information
This part contains specific recommendations for presenting and representing information on visual displays. It includes guidance on ways of representing
complex information using alphanumeric and graphical/symbolic codes, screen layout, and design as well as the use of windows.

ISO/DIS 9241-13: User guidance
This part provides recommendations for the design and evaluation of user guidance attributes of software user interfaces including Prompts, Feedback, Status, On-line Help and Error Management.

ISO/DIS 9241-14: Menu dialogues
This part provides recommendations for the ergonomic design of menus used in user-computer dialogues. The recommendations cover menu structure, navigation, option selection and execution, and menu presentation (by various techniques including windowing, panels, buttons, fields, etc.). Part 14 is intended to be used by both designers and evaluators of menus (however, its focus is primarily towards the designer).

ISO/DIS 9241-15: Command language dialogues
This part provides recommendations for the ergonomic design of command languages used in user-computer dialogues. The recommendations cover command language structure and syntax, command representations, input and output considerations, and feedback and help. Part 15 is intended to be used by both designers and evaluators of command dialogues, but the focus is primarily towards the designer.

ISO/DIS 9241-16: Direct manipulation dialogues
This part provides recommendations for the ergonomic design of direct manipulation dialogues, and includes the manipulation of objects, and the design of metaphors, objects and attributes. It covers those aspects of ŒGraphical User Interfaces¹ which are directly manipulated, and not covered by other parts of
ISO 9241. Part 16 is intended to be used by both designers and evaluators of command dialogues, but the focus is primarily towards the designer.

ISO/DIS 9241-17: Form-filling dialogues
This part provides recommendations for the ergonomic design of form filling dialogues. The recommendations cover form structure and output considerations, input considerations, and form navigation. Part 17 is intended to be used by both designers and evaluators of command dialogues, but the focus is primarily towards the designer.

ISO/IEC 10741-1 Dialogue interaction - Cursor control for text editing
This International Standard specifies how the cursor should move on the screen in response to the use of cursor control keys.

ISO/IEC DIS 11581-1 : Icon symbols and functions - Part 1: Icons - general
This part contains a framework for the development and design of icons, including general requirements and recommendations applicable to all icons.

ISO/IEC DIS 11581 - 2 : Icon symbols and functions - Part 2: Object icons
This part contains requirements and recommendations for icons that represent functions by association with an object, and that can be moved and opened. It also contains specifications for the function and appearance of 20 icons.

These standards can be used in the following ways:
To specify details of the appearance and behaviour of the user interface
To provide detailed guidance on the design of user interfaces
To provide criteria for the evaluation of user interfaces

However the attributes which a product requires for usability depend on the nature of the user, task and environment. A product has no intrinsic usability, only a capability to be used in a particular context. ISO/DIS 9241-11 can be used to help understand the context in which particular attributes can be required.

The IEEE standard 1074 for developing life cycle processes (IEEE 1991) describes the various activities that should be part of a well-managed software development process without prescribing any one particular software life-cycle. The corresponding ISO standard is ISO 12207 (ISO 1995).

The ISO draft standard ISO DIS 9241-11 (ISO 1996b) describes how to specify measurable usability criteria.

There is an ISO working group on HCI development processes. The current draft document (ISO 1996a) says "This International Standard provides guidance on human centered design activities throughout the life cycle of interactive computer-based systems. It is a tool for those managing design processes and provides guidance on sources of information and standards relevant to the human-centred approach."

The ISO 9000 series of quality standards is rapidly becoming important in industry. There are several books discussing the implications for software quality. One such reference is (Ince 1994).