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Usability Assurance


Note - work in progress

This site is under re-construction to convert the old HFIPRA site to a more general purpose site on usability assurance.

Doubtless it will continue to evolve, but right now, many of the pages are just placeholders for the final version.

This page sets out some introductory material on usability assurance, covering the goals, the background, the principles, and the underpinning standards. It concludes with some words on the logo. Readers are recommended to read the page ‘usability and glossary’ early on, at least to get an understanding of the broad scope given to the meaning of usability. 


Welcome to the website for guidance on Usability Assurance.  This page explains why Usability Assurance is invaluable to delivering systems and services that meet user needs.


The goal of usability engineering, Human System Integration (HSI), or Human Factors Integration (HFI) is to provide assurance that a system or product will be operable by those who are intended to use and maintain it.  It is not possible to tell whether a delivered complex system or product is operable just by looking at it.  Testing for all conditions of use is too expensive.  Therefore, an efficient and effective approach to assurance of operability has to be found.  If the right HSI activities are performed in the right way at the right time throughout the lifecycle they will ensure that the system or product has the best chance of being operable.  Visibility of HSI activities and outcomes provides the necessary management assurance.

Historical context

The  exam question to be answered was posed by the US General Accounting Office  (1981) "What assurances are there that weapon systems developed can be  operated and maintained by the people who must use them?"  

The  approaches developed by the GAO at that time had much merit, but their principal  weakness was that they were retrospective.   The aim of usability assurance activity since then has been to provide resources that can be both prospective and retrospective.  

For  evolutionary development, where the technology used progresses slowly, the  procurement context is stable, and where the user organisation changes only  slightly, the risks to operability are modest.   However, in situations of rapid change in technology, procurement  strategy or the user organisation, there is a significant risk that the system  will not be fully operable.   In such situations, explicit assurance becomes extremely valuable.

The work by the US Software Engineering Institute on the software Capability Maturity Model (Paulk et al 1993) noted that as technologies developed they moved away from a 'bespoke' approach to one in which methods are standardised and subject to quality assurance. The Usability Maturity Model (UMM) and the HS model represent a maturing of the Human Factors (HF) discipline.

Logic of the usability assurance approach

The  logic of the usability assurance approach is as follows:  

1. Once  a product has been fielded, it is intuitively obvious to the user whether or not  it is usable.

2. Usability can now be measured in a way that accords with our intuitions, but which is backed up by validated standards and measures.

3.  By the time we are in a position to measure usability - even on a prototype - many  of the key design decisions have been made, and options for improvement are  limited.

4. So, we need to take an early look at the organisational processes that will support  the delivery of usable products.

5. These have been defined in the Usability Maturity Model for products and in the Human Systems model for total systems, and can be used for Capability Evaluation and Process  Improvement to  provide assurance that the resulting product will be usable.

Principles of Human-Centred Design

The principles for Human-Centred Design (HCD) are:

  • the active involvement of users and a clear understanding of user and task requirements
  • an appropriate allocation of function between users and technology
  • the iteration of design solutions
  • multi-disciplinary design.

Underpinning standards

The implications of the introduction of ISO 13407 and ISO TR 18529 are profound, and potentially include liability issues. The status of ISO 13407 as a BS (British Standard) and an EN (European standard) has major implications in Europe. The European Display Screen Equipment Directive requires that the “principles of software ergonomics” are applied in the development of software.  When seeking a definition of principles it is hard to argue against an international standards.

The key standards are:

ISO  PAS 18152:2003 A specification for the process assessment of human-system issues. This is often termed the Usability Maturity Model (UMM) from which it was derived.

ISO  TR 18529:2000 Ergonomics of human system interaction - Human-centred lifecycle process descriptions.  To retain the general analogy with CMM, it has been proposed that this is called UMMi.

About the logo

The logo is an adaptation of the drawing by Leonardo da Vinci called ‘Vitruvian man’.  The HCD processes have been added to the drawing in a way that represents their use in an iterative cycle. The drawing brings together views on HCD from three periods in history. Some links on the topics are included at the end of the bibliography.

Vitruvius lived around the start of the Current Era (i.e. around the time of Christ) and was architect and builder to Caesar Augustus.  Apart from his writings on human proportions, he wrote with authority on competence for designers (and on project risk).  The HCD view of Quality In Use is concerned with effectiveness, efficiency, satisfaction and safety.  Vitruvius sought to achieve firmness, utility and delight. 

Leonardo da Vinci (and others) took Vitruvius’ writing on human proportions and used it to produce illustrations such as the one above, and also as the basis of building proportions. Designing chapels on human proportions (rather than the divine ones of golden ratios) was indicative of the Renaissance shift in putting man at the centre of things (rather than a fearsome God).

Human Centred Design tries to put people at the centre of system design and operation (rather than technology).  As practiced in the UK/US, it generally accepts much of the ethos of technology. Niels Bjorn-Anderssen (1985) raised the question of “whether all our (the HF community) intellectual capacity, energy and other precious resources are being utilized to:

  • Soften the technology to make it more compatible with human beings (through removing the flicker in order not to damage the eyes, dtaching the keyboard in order not to damage the back of the operator, making it so easy to use that “even a child or a mentaly retarded person can use it” etc.)

and in this way provide a sugar coating on the pill so that it may be swallowed more easily, or

  • whether  we are genuinely contributing to the attainment of true human values.”

The ambiguity is nicely caught in the ‘ethics’ cartoon strip by Moira Munro.

It would be possible to argue that Usability Assurance is neutral, but in Habermas’ terms, it is correct to argue that for process-based approaches, the relationship of theory to practice asserts itself as the purposive-rational application of techniques assured by empirical science (unlike some participative approaches, say).  However, it is not the direct application of techological rationality in the way that much scientist-centred usability is (see the “Usability Must Die” link).

Copyright note

Note: The material on this usability assurance site including the HFIPRA material is Copyright Lloyd’s Register of Shipping 2003 unless otherwise stated. Part of the authors' work was carried out under projects for the European Commission and the UK Ministry of Defence. The support of these bodies is gratefully acknowledged.


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