The EU Conception of the HCI Engineering general design problem is expressed informally as: ‘to design human interactions with computers for effective working.’ (C1) The EU Conception is a unitary 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 knowledge, in the form of principles, would be expressed in terms of those same concepts). (C2) (F1)
The EU Conception of the HCI Engineering design problem presupposes an associated HCI Discipline having three primary characteristics: a general problem; practices providing solutions to that problem; and knowledge supporting those practices. (C3) The EU conception of the design problem belongs to the class of general design problem and includes the design of artefacts (for example, bridges) and the design of states of the world (for example, public administration). (C4)
The EU Conception has the necessary property of a scope, delimiting the province of concern of the associated discipline of HCI Engineering. (C5) The scope includes: humans, both as individuals, groups and as social organisations. It also includes computers, both as programmable machines, stand-alone and networked, and as functionally embedded devices within machines. Its scope also includes: work, both as concerns individuals and the organisations in which it occurs.
The EU Conception categorises HCI Engineering design problems as ‘hard’ or ‘soft’. Hard and soft problems are distinguished by the need for engineering design solutions, as specified by HCI design practices, to be determinate. The design practices vary in the completeness of their specification before implementation. ‘Specify then implement’ design practices (based on formal design knowledge, such as principles) implicate more complete specification. ‘Implement and test’ design practices (based on informal design knowledge, such as guide-lines) implicate less complete specification. (C8) (F2) Taken together, the dimension of problem hardness, characterising HCI general design problems and the dimension of specification completeness, characterising HCI practices, constitute a classification space for approaches to HCI engineering, of which EU engineering is one. (C9)
The EU Conception of the HCI Engineering design problem asserts a fundamental distinction between behavioural systems, which perform work and a world in which work originates, is performed and has its consequences. (C13) Effectiveness derives from the relationship of an interactive worksystem with its domain of application, assimilating both the work performed by the worksystem and the costs it incurs. (C14) The concern of the associated HCI Engineering discipline is to design the interactive worksystem for performance. (C15). The interactive worksystem is constituted of two separate, but interacting sub-systems, that is, a system of human behaviours, interacting with a system of computer behaviours. (C16)
According to the EU Conception, the general design problem of HCI Engineering is to produce implementable designs of human behaviours, which, interacting with computer behaviours, are constituted within a worksystem, whose performance conforms with some desired performance. (C17) The interactions take place in a world in which work originates and has its consequences. (C18) This work arises at the intersection of organisations and computer technology and is expressed in terms of objects. The latter may be both abstract, as well as physical and are characterised by their attributes. (C19) Abstract attributes are of information and knowledge. Physical attributes are of energy and matter. The different attributes of an object emerge at different levels within a hierarchy of levels of complexity. (C20) Attributes of objects are related in two ways – at different levels of complexity and within those levels. (C21) Attributes have states, which change or are changed over time. Thus, objects exhibit an affordance for transformation, expressed by their attributes’ potential for change of state. (C22) A domain of application is conceptualised as: ‘a class of affordance of a class of objects’. (C23)
Following the EU Conception, organisations are conceived as having domains as their operational scope and requiring the realisation of the affordance of objects. It is a requirement satisfied by work. (C24) Organisations express their requirement for the transformation of objects by formulating goals. A product goal specifies a required transformation, realised by means of the affordance of objects. (C25) The concept of Quality describes the variance of an actual transform with that specified by a product goal. An EU HCI Engineering problem exists, when actual Quality is not equal to desired Quality. (C26) Conception of the domain is of objects, characterised by their attributes and exhibiting an affordance, arising from the potential changes of state of those attributes. (C27)
The EU Conception identifies interactive worksystems, consisting of human and computer behaviours together performing work. (C28) Humans formulate goals and their corresponding behaviors are said to be intentional (or purposeful). Computers are designed to achieve goals and their corresponding behaviours are said to be intended (or purposive). An interactive worksystem is a behavioural system distinguished by a boundary, enclosing all human and computer behaviours, whose purpose is to achieve a common goal. (C29) Worksystems achieve goals by the transformation of objects, that is, by producing state changes in the abstract and physical attributes of those objects. (C30) The behaviors of the human and computer are conceptualised as behavioral sub-systems of the worksystem – sub-systems, which interact. (C31) Behavior may be loosely understood as ‘what the user does’ in contrast with ‘what is done’, that is, attribute state changes of the domain. More precisely, the user is conceptualised as a system of distinct, but related, human behaviours identifiable as the sequence of states of a person interacting with a computer to perform work and corresponding with an intentional transformation of objects in a domain. Although possible at many levels, the user must be at least conceptualised at a level commensurate with the level of description of the transformation of objects in the domain. (C32)
In the EU Conception, worksystem behaviours are both physical and abstract. (C33) The latter process information, concerning object-attribute-state changes in the domain, whose transformation is required by goals. Physical behaviours are related to, and express, abstract behaviors. In addition, the user is conceptualised as having cognitive (knowing), conative (trying) and affective (experiencing) aspects. (C34) The user may include both on-line and off-line human behaviours. On-line behaviours are associated with the computer’s representation of the domain; 0ff-line behaviours are associated with non-computer representations of the domain or the latter itself. Conceptualisation of the user as a system of human behaviours is extended to the structures enabling behaviours. (C37) There is a one-to-many mapping between a human’s structures and the behaviours they might enable. The structures may support many different behaviours. Physical human structures are neural, biomechanical and physiological. Mental structures consist of representations and processes, which transform them, (C38)
Work performed by interactive worksystems incurs ‘resource costs’. (C39) Certain costs are associated with the user and distinguished as structural human costs and behavioural human costs. Structural human (‘set-up’ or learning) costs are incurred in the development of human skills and knowledge, as in training and education. Such costs are both mental and physical. (C40) Behavioral human costs are incurred, when the user recruits human structures to perform work. Such costs are both mental and physical. (C41)
In the EU Conception of the HCI Engineering design problem, effectiveness derives from the relationship of an interactive worksystem with its domain. Effectiveness assimilates both the quality of the work performed by the worksystem and the costs incurred by it. (C42) Quality and costs are the primary constituents of the concept of performance through which effectiveness is expressed. A desired performance of an interactive worksystem is conceptualised such that desired performance might be either absolute or relative, as in a comparative performance to be matched or improved upon. (C43) This EU Engineering Conception of performance has the following implications.
First, the quality of the transform, expressing performance, is distinguished from the effectiveness of the worksystem, which produces it. (C44) Second, optimal human behaviours are conceived as those incurring the minimum resource costs in producing a given transform. (C45) Third, common measures of ‘human performance’ – such as ‘time and errors’- are related to performance, as conceived here. (46) Errors may increase resource costs and/or reduce quality. The time taken by human behaviours may (very generally) be associated with increased user costs. Fourth, structural and behavioural human costs may be traded off in performance. (C47) Finally, fifth, user and computer costs may also be traded off. (C48) This concludes a summary of the EU Conception of the HCI Engineering design problem.
The Conception is a unitary view of the necessary concepts and their relations to express that design problem and so, any design solution. In addition, it is a pre-requisite for developing formal HCI Engineering design knowledge as principles to support ‘specify then implement’ HCI engineering design practices. A complete version of the Conception can be found in the short and full versions of the Dowell and Long (1989) original paper – see 2.4 and 2.5.
Key concepts are shown in bold on their first appearance only.