Interacción hombre-máquina

Proceedings of the 6th International Conference on Human Computer Interaction, Yokohama, July 1995. Anzai & Ogawa (eds), Elsevier.

Human-Computer Interaction Standards
Nigel Bevan NPL Usability Services, National Physical Laboratory, Teddington, Middx, TW11 0LW, UK Nigel@hci.npl.co.uk

1. DIFFERENT APPROACHES TO STANDARDS FOR HCI It is often assumed that a standard means a precisespecification. Such standards have brought benefits in many fields, eg: bolts which screw into nuts, ATMs which can read credit cards, and compilers which can read programming languages. Some HCI standards are also of this type: many design guides provide a detailed specification of the nature of the user interface. Although standard user interfaces provide the benefit of consistency, they become out ofdate as technology changes, and are usually only appropriate for limited types of users and tasks (Bevan and Holdaway, 1993). Thus most work on international standards for HCI has not been about precise specification, but instead has concentrated on the principles which need to be applied in order to produce an interface which meets user and task needs. These standards broadly fall into twocategories. One is a "top-down" approach which is concerned with usability as a broad quality objective: the ability to use a product for its intended purpose. The other is a product-oriented "bottom-up" view which is concerned with aspects of the interface which make a system easier to use. The broad quality view originates from human factors, and standards of this type are applicable in the broadcontext of design and quality objectives. The product-oriented view concentrates on the design of specific attributes, and relates more closely to the needs of the interface designer and the role of usability in software engineering (see Bevan, 1995). Section 4 explains how standards can be used to provide a means of meeting the requirements for the operator-computer interface in the European Directiveon Display Screen Equipment.
1.1 Usability as a quality objective

These standards relate to usability as a high level quality objective, and usability is defined in this way in ISO 9241-11: 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. Standards of this type canbe used to support the following activities: • specification of overall quality and usability requirements and evaluation against these requirements (ISO 9241-11 and ISO/IEC 14598-1) • incorporation of usability into a quality system (ISO 9241-11) • incorporation of usability into the design process (ISO/IEC 13407) Section 2 describes these standards.

1.2 Product-oriented standards

In theproduct-oriented view, usability is seen as one relatively independent contribution to software quality, and is defined in this way in ISO/IEC 9126: Usability: a 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 users. Section 3 describes standards which deal with usability in terms of attributes whichmust be designed into a software product to make it easy to use: ISO 9241: Ergonomics requirements for office work with visual display terminals: Part 10, 12-17: dialogue design ISO/IEC 10741-1 Dialogue interaction - Cursor control for text editing ISO/IEC 11581 Icon symbols and functions ISO/IEC 9126 Software product evaluation - Quality characteristics and guidelines for their use These standardscan 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...