John

Towards a Conception for an Engineering Discipline of Human Factors

Short version

John Dowell and John Long

Ergonomics Unit, University College London, 

26, Bedford Way, London. WC1H 0AP. 

Abstract  ……… The paper is in two parts. Part I examines the potential for Human Factors to formulate engineering principles. …….. A conception would provide the set of related concepts which both expressed the general design problem more formally, and which might be embodied in engineering principles.

In P. Barber and J. Laws (ed.s) Special Issue on Cognitive Ergonomics, Ergonomics, 1989, vol. 32, no. 11, pp. 1613-1536.

Part I. Requirement for Human Factors as an Engineering Discipline of Human-Computer Interaction

1.1 Introduction;

1.2 Characterization of the human factors discipline;

1.3 State of the human factors art;

1.4 Human factors engineering;

1.5 The requirement for an engineering conception of human factors.

1.1 Introduction

Assessment of contemporary HF (Section 1.3.) concludes that its practices are predominantly those of a craft. Shortcomings of those practices are exposed which indict the absence of support from appropriate formal discipline knowledge. This absence prompts the question as to what might be the formal knowledge which HF could develop, and what might be the process of its formulation. By comparing the HF general design problem with other, better understood, general design problems, and by identifying the formal knowledge possessed by the corresponding disciplines, the potential for HF engineering principles is suggested (Section 1.4.).

However, a pre-requisite for the formulation of any engineering principle is a conception. A conception is a unitary (and consensus) view of a general design problem; its power lies in the coherence and completeness of its definition of the concepts which can express that problem. Engineering principles are articulated in terms of those concepts. Hence, the requirement for a conception for the HF discipline is concluded (Section 1.5.).

1.2. Characterisation of the Human Factors Discipline

Most definitions of disciplines assume three primary characteristics: a general problem; practices, providing solutions to that problem; and knowledge, supporting those practices.

1.3. State of the Human Factors Art

It would be difficult to reject the claim that the contemporary HF discipline has the character of a craft …….. Characteristic of a craft, the execution and success of its practices in systems development depends principally on the expertise, guided intuition and accumulated experience which the practitioner brings to bear on the design problem.

……..

The dogma of HF as necessarily a craft whose knowledge may only be the accrued experience of its practitioners, is nowhere presented rationally.

……Third, HF practices are inefficient. Each development of a system requires the solving of new problems by implementation then testing. There is no formal structure within which experience accumulated in the successful development of previous systems can be recruited to support solutions to the new problems, except through the memory and intuitions of the designer. These may not be shared by others, except indirectly (for example, through the formulation of heuristics), and so experience may be lost and may have to be re-acquired (Long and Dowell, 1989).

The guidance may be direct – by the designer’s familiarity with psychological theory and practice, or may be indirect by means of guidelines derived from psychological findings. In both cases, the guidance can offer only advice, which must be implemented then tested to assess its effectiveness. Since the general scientific problem is the explanation and prediction of phenomena, and not the design of artifacts, the guidance cannot be directly embodied in design specifications which offer a guarantee with respect to the effectiveness of the implemented design.

…….. These four deficiencies are endemic to the craft nature of contemporary HF practice. They indict the tacit HF discipline knowledge consisting of accumulated experience embodied in procedures, even where that experience has been influenced by guidance offered by the science of psychology .Because the knowledge is tacit (i.e., implicit or informal), it cannot be operationalised, and hence the role of HF in systems development cannot be planned as would be necessary for the proper integration of the knowledge. Without being operationalised, its knowledge cannot be tested, and so the efficacy of the practices it supports cannot be guaranteed. Without being tested, its knowledge cannot be generalised for new applications and so the practices it can support will be inefficient. Without being operationalised, testable, and general, the knowledge cannot be developed in any structured way as required for supporting the systematic and intentional progress of the HF discipline.

It would be incorrect to assume the current absence of formality of HF knowledge to be a necessary response to the indeterminism of human behaviour………. The extent to which human behaviour is deterministic for the purposes of designing interactive computer-based systems needs to be independently established. Only then might it be known if HF discipline knowledge could be formal.

1.4. Human Factors Engineering Principles

HF has been viewed earlier (Section 1.2.) as comparable to other disciplines which address general design problems: for example, Civil Engineering and Health Administration. The nature of the formal knowledge of a future HF discipline might, then, be suggested by examining such disciplines. The general design problems of different disciplines, however, must first be related to their characteristic practices, in order to relate the knowledge supporting those practices.

……..

there exists no pre-ordained relationship between the formality of a discipline’s knowledge and the hardness of its general design problem. In particular, the practices of a (craft) discipline supported by experience – that is, by informal knowledge – may address a hard problem. But also, within the boundary of determinism, that discipline could acquire formal knowledge to support specification as a design practice.

…….. Generally, the established engineering disciplines possess formal knowledge: a corpus of operationalised, tested, and generalised principles. Those principles are prescriptive, enabling the complete specification of design solutions before those designs are implemented (see Dowell and Long, 1988b). This theme of prescription in design is central to the thesis offered here.

Engineering principles can be substantive or methodological (see Checkland, 1981; Pirsig, 1974). Methodological Principles prescribe the methods for solving a general design problem optimally. For example, methodological principles might prescribe the representations of designs specified at a general level of description and procedures for systematically decomposing those representations until complete specification is possible at a level of description of immediate design implementation (Hubka, Andreason and Eder, 1988). Methodological principles would assure each lower level of specification as being a complete representation of an immediately higher level.

Substantive Principles prescribe the features and properties of artefacts, or systems that will constitute an optimal solution to a general design problem. As a simple example, a substantive principle deriving from Kirchoff’s Laws might be one which would specify the physical structure of a network design (sources, resistances and their nodes etc) whose behaviour (e.g., distribution of current) would constitute an optimal solution to a design problem concerning an amplifier’s power supply.

1.5. The Requirement for an Engineering Conception for Human Factors

The contemporary HF discipline does not possess either methodological or substantive engineering principles. The heuristics it possesses are either ‘rules of thumb’ derived from experience or guidelines derived from psychological theories and findings. Neither guidelines nor rules of thumb offer assurance of their efficacy in any given instance, and particularly with regard to the effectiveness of a design. The methods and models of HF (as opposed to methodological and substantive principles) are similarly without such an assurance. Clearly, any evolution of HF as an engineering discipline in the manner proposed here has yet to begin. There is an immediate need then, for a view of how it might begin, and how formulation of engineering principles might be precipitated.

……..Such a conception is a unitary (and consensus) view of the general design problem of a discipline. Its power lies in the coherence and completeness of its definition of concepts which express that problem. Hence, it enables the formulation of engineering principles which embody and instantiate those concepts. A conception (like a paradigm) is always open to rejection and replacement.

…….. It is inconceiveable that a formulation of HF engineering principles might occur whilst there is no consensus understanding of the concepts which they would embody. Articulation of a conception must then be a pre-requisite for formulation of engineering principles for HF.

Part II. Conception for an Engineering Discipline of Human Factors 

2.1 Conception of the human factors general design problem;

2.2 Conception of work and user; 2.2.1 Objects and their attributes; 2.2.2 Attributes and levels of complexity; 2.2.3 Relations between attributes; 2.2.4 Attribute states and affordance; 2.2.5 Organisations, domains (of application)2.2.6 Goals; 2.2.7 Quality; 2.2.8 Work and the user; and the requirement for attribute state changes;

2.3 Conception of the interactive worksystem and the user; 2.3.1 Interactive worksystems; 2.3.2 The user as a system of mental and physical human behaviours; 2.3.3 Human-computer interaction; 2.3.4 On-line and off-line behaviours; 2.3.5 Human structures and the user; 2.3.6 Resource costs and the user;

2.4 Conception of performance of the interactive worksystem and the user;

2.5 Conclusions and the prospect for Human Factors engineering principles

2.5. Conclusions and the Prospect for Human Factors Engineering Principles

…….. The extent to which HF engineering principles might be realiseable in practice remains to be seen. It is not supposed that the development of effective systems will never require craft skills in some form, and engineering principles are not seen to be incompatible with craft knowledge, particularly with respect to their instantiation (Long and Dowell, 1989). At a minimum, engineering principles might be expected to augment the craft knowledge of HF professionals. Yet the great potential of HF engineering principles for the effectiveness of the discipline demands serious consideration. References Ashby W. Ross, (1956), An Introduction to Cybernetics. London: Methuen.

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This paper has greatly benefited from discussion with others and from their criticisms. We would like to thank our collegues at the Ergonomics Unit, University College London and in particular, Andy Whitefield, Andrew Life and Martin Colbert. We would also like to thank the editors of the special issue for their support and two anonymous referees for their helpful comments. Any remaining infelicities – of specification and implementation – are our own

John Long and John Dowell

…….. First, consideration of disciplines in general suggests their complete definition can be summarised as: ‘knowledge, practices and a general problem having a particular scope, where knowledge supports practices seeking solutions to the general problem’. Second, the scope of the general problem of HCI is defined by reference to humans, computers, and the work they perform. Third, by intersecting these two definitions, a framework is proposed within which different conceptions of the HCI discipline may be established, ordered, and related. The framework expresses the essential characteristics of the HCI discipline, and can be summarised as: ‘the use of HCI knowledge to support practices seeking solutions to the general problem of HCI’. ……..

Published in: People and Computers V. Sutcliffe A. and Macaulay L. (ed.s). Cambridge University Press, Cambridge. Proceedings of the Fifth Conference of the BCS HCI SIG, Nottingham 5-8 September 1989.

Contents

1. Introduction

1.1. Alternative Interpretations of the Theme

1.2. Alternative Conceptions of HCI: the Requirement for a Framework

1.3. Aims

2. A Framework for Conceptions of the HCI Discipline

2.1. On the Nature of Disciplines

2.2. Of Humans Interacting with Computers

2.3. The Framework for Conceptions of the HCI Discipline

3. Three Conceptions of the Discipline of HCI

3.1. Conception of HCI as a Craft Discipline

3.2. Conception of HCI as an Applied Science Discipline

3.3. Conception of HCI as an Engineering Discipline

4. Summary and Conclusions

1. Introduction

1.1. Alternative Interpretations of the Theme

1.2. Alternative Conceptions of HCI: the Requirement for a Framework

1.3. Aims

2. A Framework for Conceptions of the HCI Discipline

2.1. On the Nature of Disciplines

Most definitions assume three primary characteristics of disciplines: knowledge; practice; and a general problem.

All definitions of disciplines make reference to discipline knowledge as the product of research or more generally of a field of study. …….. Knowledge, therefore, is a necessary characteristic of a discipline.

Consideration of different disciplines suggests that practice is also a necessary characteristic of a discipline. Further, a discipline’s knowledge is used by its practices to solve a general (discipline) problem. For example, the discipline of science includes the scientific practice addressing the general (scientific) problem of explanation and prediction. The discipline of engineering includes the engineering practice addressing the general (engineering) problem of design. The discipline of medicine includes the medical practice addressing the general (medical) problem of supporting health. Practice, therefore, and the general (discipline) problem which it uses knowledge to solve, are also necessary characteristics of a discipline.

…….. Taken together, the three necessary characteristics of a discipline (and the two basic properties additionally concluded), suggest the definition of a discipline as: ‘the use of knowledge to support practices seeking solutions to a general problem having a particular scope’. It is represented schematically in Figure 1. This definition will be used subsequently to express HCI.

2.2. Of Humans Interacting with Computers

2.3. The Framework for Conceptions of the HCI Discipline

…….. Given the definition of its scope (above), and the preceding definition of disciplines, the general problem addressed by the discipline of HCI is asserted as: ‘the design of humans and computers interacting to perform work effectively’. It is a general (discipline) problem of design : its ultimate product is designs. The practices of the HCI discipline seek solutions to this general problem, for example: in the construction of computer hardware and software; in the selection and training of humans to use computers; in aspects of the management of work, etc. HCI discipline knowledge supports the practices that provide such solutions.

…….. Hence, we may express a framework for conceptions of the discipline of HCI as:

‘the use of HCI knowledge to support practices seeking solutions to the general problem of HCI of designing humans and computers interacting to perform work effectively. HCI knowledge is constituted of HF knowledge and SE knowledge, respectively supporting HF practices and SE practices. Those practices respectively address the HF general problem of the design of humans interacting with computers, and the SE general problem of the design of computers interacting with humans’. The framework is represented schematically in Figure 3.

3. Three Conceptions of the Discipline of HCI

3.1. Conception of HCI as a Craft Discipline

Craft disciplines solve the general problems they address by practices of implementation and evaluation. Their practices are supported by knowledge typically in the form of heuristics; heuristics are implicit (as in the procedures of good practice) and informal (as in the advice provided by one craftsperson to another). Craft knowledge is acquired by practice and example, and so is experiential; it is neither explicit nor formal. Conception of HCI as a craft discipline is represented schematically in Figure 4.

HCI craft knowledge, supporting practice, is maintained by practice itself. For example, in the case of Videotex shopping, users often fail to cite on the order form the reference number of the goods they wish to purchase. A useful design heuristic is to try prompting users with the relevant information, for example, by reminding them on the screen displaying the goods that the associated reference number is required for ordering and should be noted. An alternative heuristic is to try re-labelling the reference number of the goods, for example to ‘ordering’ rather than reference number. Heuristics such as these are formulated and tried out on new implementations and are retained if associated with successful interactions.

In summary, the design of Ded by Bornat and Thimbleby illustrates the critical features of HCI as a craft discipline. They addressed the specific form of the general problem (general because their colleague suggested part of the solution – one ‘mode’ – and because their heuristics were made available to others practising the craft discipline). Their practices involved the iterative implementation and evaluation of the computer interacting with the human, and of the human interacting with the computer. They were supported by craft discipline heuristics – for example: ‘simple operations should be simple, and the complex possible’. Such craft knowledge was either implicit or informal; the concepts of ‘simple’ and ‘complex’ remaining undefined, together with their associated operations (the only definitions being those implicit in Ded and in the expertise of Bornat and Thimbleby, or informal in their report). And finally, the heuristics were generated for a purpose, tried out for their adequacy (in the case of Ded) and then retained or discarded (for further application to Ded). This too is characteristic of a craft discipline. Accepting that Ded met its requirements for both functionality (enter text, review text, etc.) and for usability (use straight away, etc) – as claimed by Bornat and Thimbleby – it can be accepted as an example of good HCI craft practice.

3.2. Conception of HCI as an Applied Science Discipline

An applied science discipline is one which recruits scientific knowledge to the practice of solving its general problem – a design problem. HCI as an applied science discipline uses scientific knowledge as an aid to addressing the general problem of designing humans and computers interacting to perform work effectively. HCI as an applied science is represented schematically in Figure 5.

3.3. Conception of HCI as an Engineering Discipline

The discipline of engineering may characteristically solve its general problem (of design) by the specification of designs before their implementation. It is able to do so because of the prescriptive nature of its discipline knowledge supporting those practices – knowledge formulated as engineering principles. Further, its practices are characterised by their aim of ‘design for performance’. Engineering principles may enable designs to be prescriptively specified for artefacts, or systems which when implemented, demonstrate a prescribed and assured performance. And further, engineering disciplines may solve their general problem by exploiting a decompositional approach to design. Designs specified at a general level of description may be systematically decomposed until their specification is possible at a level of description of their complete implementation. Engineering principles may assure each level of specification as a representation of the previous level.

The concepts described enable the expression of the general problem addressed by an engineering discipline of HCI as: specify then implement user behaviour {U} and computer behaviour {C}, such that {U} interacting with {C} constitutes an interactive worksystem exhibiting desired performance (PD). It is implicit in this expression that the specification of behaviour supposes and enables specification of the structure supporting that behaviour. HCI engineering principles are conceptualised as supporting the practices of an engineering HCI discipline in specifying implementable designs for the interacting behaviours of both the user and computer that would achieve PD.

Given the independence of their principles, the engineering disciplines of SE and HF might each pursue their own practices, having commensurate and integrated roles in the development of interactive worksystems. Whilst SE specified and implemented the interacting behaviours of computers, HF would specify and implement the interacting behaviours of users. Together, the practices of SE and HF would aim to produce interactive worksystems which achieved PD.

4. Summary and Conclusions

The proposal made here is that the general problem of HCI is the design of humans and computers interacting to perform work effectively. The qualification of the general problem as ‘design’, and the addition to the scope of that problem of ‘…. to perform work effectively’, has important consequences for the different conceptions of HCI (see Section 3). For example, since design is not the general problem of science, scientific knowledge (for example, psychology or computer science) cannot be recruited directly to the practice of solving the general problem of design (see Barnard, Grudin & Maclean [1989]). Further, certain attempts to develop complete engineering principles for HCI fail to qualify as such, because they make no reference to ‘…. to perform work effectively’ (Dix & Harrison [1987]; Thimbleby [1984]).

Finally, generalisation of the Conference theme has identified two conceptions of HCI as a discipline as alternatives to the applied science conception implied by the theme. The other two conceptions are HCI as a craft discipline and HCI as an engineering discipline. Although all three conceptions address the general problem of HCI, they differ concerning the knowledge recruited to solve the problem. Craft recruits heuristics; applied science recruits theories expressed as guidelines; and engineering recruits principles. They also differ in the practice they espouse to solve the general problem. Craft typically implements, evaluates and iterates (Bornat & Thimbleby [1989]); applied science typically selects guidelines to inform implementation, evaluation and iteration (although guidelines may also be generated on the basis of extant knowledge, e.g. – Hammond & Allinson [1988]); and engineering typically would specify and then implement (Dowell & Long [1988]).

The different types of knowledge and the different types of practice have important consequences for the effectiveness of any discipline of HCI. Heuristics are easy to generate, but offer no guarantee that the design solution will exhibit the properties of performance desired. Scientific theories are difficult and costly to generate, and the guidelines derived from them (like heuristics) offer no final guarantee concerning performance. Engineering principles would offer guarantees, but are predicted to be difficult, costly and slow to develop.

Lastly, Carroll and Campbell’s claim (Carroll & Campbell [1988]) that HCI research has been more successful at developing methodology than theory can be explicated by the need for guidelines to express psychological knowledge and the need to validate those guidelines formally, and the absence of engineering principles, plus the importation of psychology research methods into HCI and the simulation of good (craft) practice. The methodologies, however, are not methodological principles which guarantee the solution of the design problem (Dowell & Long [manuscript submitted for publication]), but procedures to be tailored anew in the manner of a craft discipline. Thus, relating the conceptions of HCI as a set of possible disciplines provides insight into whether HCI research has been more successful at developing methodologies than theories.

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Acknowledgement. This paper has greatly benefited from discussion with others and from their criticisms. In particular, we would like to thank: Andy Whitefield and Andrew Life, colleagues at the Ergonomics Unit, University College London; Charles Brennan of Cambridge University, and Michael Harrison of York University; and also those who attended a seminar presentation of many of these ideas at the MRC Applied Psychology Unit, Cambridge. The views expressed in the paper, however, are those of the authors.

Footnotes:

1. Notwithstanding the so-called ‘hierarchy theory ‘ which assumes a phenomenon to occur at a particular level of complexity and to subsume others at a lower level (eg, Pattee, 1973).