Engineering Framework

This framework for a discipline of HCI as engineering is more complete, coherent and fit-for-purpose than the description afforded by the engineering approach to HCI (see earlier). The framework thus better supports thinking about and doing engineering HCI. As the framework is explicit, it can be shared by all interested researchers. Once shared, it enables researchers to build on each other’s work. This sharing and building is further supported by a re-expression of the framework, as a design research exemplar. The latter specifies the complete design research cycle, which once implemented constitutes a case-study of an of an engineering approach to HCI. The diagram, which follows, presents the engineering design research exemplar.

Examples of such levels are presented here – first a short version and then a long version. Researchers, of course, might have their own lower level descriptions or subscribe to some more generally recognised levels. Such descriptions are acceptable, as long as they fit with the higher level descriptions of the framework and are complete; coherent and fit-for-purpose. In the absence of alternative levels of description, researchers might try the short version first .

These levels go, for example from ‘human’ to ‘user’ and from ‘computer’ to ‘interactive system’. The lowest level, of course, needs to reference the application, in terms of the application itself but also the interactive system. Researchers are encouraged to select from the framework extensions as required and to add the lowest level description, relevant to their research. The lowest level is used here to illustrate the extended engineering framework.

Following the Engineering Design Research exemplar diagram, researchers need to specify:

• User Requirements (unsatisfied) and Interactive System;
• Design Problem and Design Solution for design guidelines/models and methods Engineering Knowledge;
• Specific Principle Design Problem and Specific Principle Design Solution for Specific Substantive and Methodological Principle Engineering Knowledge;
•  General Principle Design Problem and General Principle Design Solution for General Substantive and Methodological Principle Engineering Knowledge;

These specifications require the extended Engineering framework to include: the Application; the Interactive System; and Performance, relating the former to the latter. Engineering design requires the Interactive System to perform tasks (the Application) as effectively as desired (Performance). Engineering Research acquires and validates Engineering Knowledge to support Engineering Design Practices.

The Engineering Framework Extension, thus includes: Application; Interactive System; and Performance.

1. Engineering Applications

1.1 Objects

Engineering applications (the tasks, which the interactive system performs) can be described in terms of objects. Objects may be both abstract and physical and are characterised by their attributes. Abstract attributes are those of information and knowledge. Physical attributes are those of energy and matter.

For example, a website application (such as for an academic organisation) can be described for design research purposes in terms of objects; their abstract attributes, supporting the creation of websites; their physical attributes supporting the visual/verbal representation of displayed information on the website pages by means of text and images. Application objects are specified as part of engineering design and can be researched as such.

1.2 Attributes and Levels

The attributes of an engineering application object emerge at different levels of description. For example, characters and their configuration on a webpage are physical attributes of the object ‘webpage’, which emerge at one level. The message on the page is an abstract attribute, which emerges at a higher level of description.

1.3 Relations between Attributes

Attributes of an engineering application object are related in two ways. First, attributes are related at different levels of complexity. Second, attributes are related within levels of description. Such relations are specified as part of engineering design.

1.4 Attribute States and Affordance

The attributes of engineering application objects can be described as having states. Further, those states may change. For example, the content and characters (attributes) of a website page (object) may change state: the content with respect to meaning and grammar; its characters with respect to size and font. Objects exhibit an affordance for transformation, associated with their attributes’ potential for state change.

1.5 Applications and the Requirement for Attribute State Changes

An engineering application may be described in terms of affordances. Accordingly, an object may be associated with a number of applications. The object ‘website’ may be associated within the application as that of site structure (state changes of its organisational attributes) and the authorship (state changes of its textual and image content). In principle, an application may have any level of generality, for example, the writing of personal pages and the writing of academic pages.

Organisations have applications and require the realisation of the affordance of their associated objects. For example, ‘completing a survey’ and ‘writing for a special group of users’, may each have a website page as their transform, where the pages are objects, whose attributes (their content, format and status, for example) have an intended state. Further editing of those pages would produce additional state changes, and therein, new transforms. Requiring new affordances might constitute an additional (unsatisfied) User Requirement and result in a new Interactive System.

1.6 Application Goals

The requirement for the transformation of engineering application objects is expressed in the form of goals. A product goal specifies a required transform – the realisation of the affordance of an object. A product goal supposes necessary state changes of many attributes. The requirement of each attribute state change can be expressed as an application task goal, derived from the product goal.

So, for example, the product goal demanding transformation of a website page, making its messages less complex and so more clear, would be expressed by task goals, possibly requiring state changes of semantic attributes of the propositional structure of the text and images and of associated syntactic attributes of the grammatical structure. Hence, a product goal can be re-expressed as an application task goal structure, a hierarchical structure expressing the relations between task goals, for example, their sequences. The latter might constitute part of an engineering design, calling upon engineering knowledge as: design guidelines/models and methods/specific design principles/general design principles.

1.7 Engineering Application as: performing tasks effectively, as desired.

The transformation of an object, associated with a product goal, involves many attribute state changes – both within and across levels of complexity. Consequently, there may be alternative transforms, which satisfy a product goal – website pages with different styles. The concept of ‘performing tasks effectively, as desired’ describes the variance of an actual transform with that specified by a product goal.

1.8 Engineering Application and the User

One description of the application then, is of objects, characterised by their attributes, and exhibiting an affordance, arising from the potential changes of state of those attributes. By specifying product goals, users express their requirement for transforms – objects with specific attribute states. Transforms are produced by ‘performing tasks effectively, as desired’.

From product goals is derived a structure of related task goals, which can be assigned, by engineering design practice, either to the user or to the interactive computer (or both) within an associated interactive system. Task goals assigned to the user by engineering design are those, intended to motivate the user’s behaviours. The actual state changes (and therein transforms), which those behaviours produce, may or may not be those specified by task and product goals, a difference expressed by the concept ‘as desired’, characterised in terms of: wanted/needed/experienced/felt/valued.

2.Engineering Interactive Computers

2.1 Interactive Systems

An interactive system can be described as a behavioural system, distinguished by a boundary enclosing all human and interactive computer behaviours, whose purpose is to achieve and satisfy a common goal. For example, the behaviours of a webmaster, using a website application, whose purpose is to construct websites, constitute an interactive system. Critically, it is only by identifying the common goal, that the boundary of the interactive system can be established and so designed and researched.

Interactive systems transform objects by producing state changes in the abstract and physical attributes of those objects (see 1.1). The webmaster and the website application may transform the object ‘page’ by changing both the attributes of its meaning and the attributes of its layout, both text and images.

The behaviours of the human and the interactive computer are described as behavioural sub-systems of the interactive system – sub-systems, which interact. The human behavioural sub-system is more specifically termed the user. Behaviour may be loosely understood as ‘what the human does’, in contrast with ‘what is done’ (i.e. attribute state changes of application objects).

Although expressible at many levels of description, the user must at least be described at a level, commensurate with the level of description of the transformation of application objects. For example, a webmaster interacting with a website application is a user, whose behaviours include receiving and replying to messages, sent to the website.

2.2 Humans as a System of Mental and Physical Behaviours

The behaviours, constituting an interactive system, are both physical and abstract. Abstract behaviours are generally the acquisition, storage, and transformation of information. They represent and process information, at least concerning: application objects and their attributes, attribute relations and attribute states and the transformations, required by goals. Physical behaviours are related to, and express, abstract behaviours.

Accordingly, the user is described as a system of both mental (abstract) and overt (physical) behaviours. They are related within an assumed hierarchy of behaviour types (and their control), wherein mental behaviours generally determine, and are expressed by, overt behaviours. Mental behaviours may transform (abstract) application objects, represented in cognition or express, through overt behaviour, plans for transforming application objects.

For example, a webmaster has the product goal, required to maintain the circulation of a website newsletter to a target audience. The webmaster interacts with the computer by means of the user interface (whose behaviours include the transmission of information in the newsletter). Hence, the webmaster acquires a representation of the current circulation by collating the information displayed by the computer screen and assessing it by comparison with the conditions, specified by the product goal. The webmaster reasons about the attribute state changes, necessary to eliminate any discrepancy between current and desired conditions of the process, that is, the set of related changes, which will produce and circulate the newsletter, ‘as desired’. That decision is expressed in the set of instructions issued to the interactive computer through overt behaviour – selecting menu options, for example.

2.3 Human-Computer Interaction

Although user and interactive computer behaviours may be described as separable sub-systems of the interactive system, these sub-systems extert a ‘mutual influence’ or interaction. Their configuration principally determines the interactive system and engineering design and research.

Interaction is described as: the mutual influence of the user (i.e. behaviours) and the interactive computer (i.e behaviours), associated within an interactive system. For example, the behaviours of a webmaster interact with the behaviours of a website application. The webmaster’s behaviours influence the behaviours of the interactive computer (access the image function), while the behaviours of the interactive computer influence the selection behaviour of the webmaster (among possible image types). The design of their interaction – the webmaster’s selection of the image function, the computer’s presentation of possible image types – determines the interactive system, comprising the webmaster and interactive computer behaviours in their planning and control of webpage creation. The interaction may be the object of engineering design and so design research.

The assignment of task goals by design then, to either the user or the interactive computer, delimits the former and therein specifies the design of the interaction. For example, replacement of an inappropriate image, required on a page is a product goal, which can be expressed as a task goal structure of necessary and related attribute state changes. In particular, the field for the appropriate image as an attribute state change in the spacing of the page. Specifying that state change may be a task goal assigned to the user, as in interaction with the behaviours of early image editor designs or it may be a task goal assigned to the interactive computer, as in interaction with the GUI ‘fill-in’ behaviours. Engineering design research would be expected to have contributed to the latter . The assignment of the task goal of specification constitutes the design of the interaction of the user and interactive computer behaviours in each case, which in turn may become the object of research.

2.4 Human Resource Costs

‘Performing tasks effectively, as desired’ by means of an interactive system always incurs resource costs. Given the separability of the user and the interactive computer behaviours, certain resource costs are associated with the user and distinguished as behavioural user costs.

Behavioural user costs are the resource costs, incurred by the user (that is, by the implementation of behaviours) to effect an application. They are both physical and mental. Physical costs are those of physical behaviours, for example, the costs of using the mouse and of attending to a screen display; they may be expressed for engineering design purposes as physical workload. Mental behavioural costs are the costs of mental behaviours, for example, the costs of knowing, reasoning, and deciding; they may be expressed for engineering design purposes as mental workload. Mental behavioural costs are ultimately manifest as physical behavioural costs.

3. Performance of the Engineering Interactive Computer System and the User.

‘To perform tasks effectively, as desired’ derives from the relationship of an interactive system with its application. It assimilates both how well the application is performed by the interactive system and the costs incurred by it. These are the primary constituents of ‘performing tasks effectively as desired’, that is, performance. They can be further differentiated, for example, as wanted/needed/experienced/felt/valued. Desired performance is the object of engineering design.

Behaviours determine performance. How well an application is performed by an interactive system is described as the actual transformation of application objects with regard to the transformation, demanded by product goals. The costs of carrying out an application are described as the resource costs, incurred by the interactive system and are separately attributed to the user and the interactive computer.

‘Performing tasks effectively as desired’ by means of an interactive system may be described as absolute or as relative, as in a comparison to be matched or improved upon. Accordingly, criteria expressing ‘as desired’ may either specify categorical gross resource costs and how well an application is performed or they may specify critical instances of those factors to be matched or improved upon. They are the object of engineering design and so of design research.

The common measures of human ‘performance’ – errors and time, are related in this notion of performance. Errors are behaviours, which increase resource costs, incurred in producing a given transform or which reduce the goodness of the transform or both. The duration of user behaviours may (very generally) be associated with increases in behavioural user costs.

Following the Engineering Design Research exemplar diagram, researchers need to specify:

User Requirements (unsatisfied) and Interactive System;
Design Problem and Design Solution for design guidelines/models and methods Engineering Knowledge;
Specific Principle Design Problem and Specific Principle Design Solution for Specific Substantive and Methodological Principle Engineering Knowledge;
General Principle Design Problem and General Principle Design Solution for General Substantive and Methodological Principle Engineering Knowledge;

These specifications require the extended Engineering framework to include: the Application; the Interactive System; and Performance, relating the former to the latter. Engineering design requires the Interactive System to perform task effectively (the Application) as desired (Performance). Engineering Research acquires and validates Engineering Knowledge to support Engineering Design Practice.

TheEngineering Framework Extension, thus includes: Application; Interactive System; and Performance.

1 Engineering Applications

1.1 Objects

Engineering applications (the ‘tasks’ the interactive system ‘performs effectively’) can be described as objects. Such applications occur in the need of organisations for interactive systems. Objects may be both abstract and physical and are characterised by their attributes. Abstract attributes are those of information and knowledge. Physical attributes are those of energy and matter.

For example, a website application (such as for an academic organisation) can be described for design research purposes in terms of objects; their abstract attributes, supporting the creation of websites; their physical attributes supporting the visual/verbal representation of displayed information on the website pages by means of text and images. Application objects are specified as part of engineering design and can be researched as such.

1.2 Attributes and Levels

The attributes of an engineering application object emerge at different levels of description. For example, characters and their configuration on a webpage are physical attributes of the object ‘webpage’, which emerge at one level. The message on the page is an abstract attribute, which emerges at a higher level of description.

1.3 Relations between Attributes

Attributes of engineering application objects are related in two ways. First, attributes are related at different levels of complexity. Second, attributes are related within levels of description.

1.4 Attribute States and Affordance

The attributes of engineering application objects can be described as having states. Further, those states may change. For example, the content and characters (attributes) of a website page (object) may change state: the content with respect to meaning and grammar; its characters with respect to size and font. Objects exhibit an affordance for transformation, associated with their attributes’ potential for state change.

1.5 Applications and the Requirement for Attribute State Changes

An engineering application may be described in terms of affordances. Accordingly, an object may be associated with a number of applications. The object ‘website’ may be associated within the application as that of site structure (state changes of its organisational attributes) and the authorship (state changes of its textual and image content). In principle, an application may have any level of generality, for example, the writing of personal pages and the writing of academic pages.

Organisations have applications and require the realisation of the affordance of their associated objects. For example, ‘completing a survey’ and ‘writing for a special group of users’, may each have a website page as their transform, where the pages are objects, whose attributes (their content, format and status, for example) have an intended state. Further editing of those pages would produce additional state changes, and therein, new transforms. Requiring new affordances might constitute an additional (unsatisfied) User Requirement and result in a new Interactive System.

1.6 Application Goals

Organisations express the requirement for the transformation of engineering application objects in terms of goals. A product goal specifies a required transform – the realisation of the affordance of an object. A product goal generally supposes necessary state changes of many attributes. The requirement of each attribute state change can be expressed as an application task goal, derived from the product goal.

So, for example, the product goal demanding transformation of a website page, making its messages less complex and so more clear, would be expressed by task goals, possibly requiring state changes of semantic attributes of the propositional structure of the text and images and of associated syntactic attributes of the grammatical structure. Hence, a product goal can be re-expressed as an application task goal structure, a hierarchical structure expressing the relations between task goals, for example, their sequences. The latter might constitute part of an engineering design, calling upon engineering knowledge as: design guidelines/models and methods/specific design principles/general design principles.

The transformation of an object, associated with a product goal, involves many attribute state changes – both within and across levels of complexity. Consequently, there may be alternative transforms, which satisfy the same product goal – e-mails with different styles, for example, where different transforms exhibit different compromises between attribute state changes of the application object. There may also be transforms, which fail to meet the product goal. The concept of ‘performing tasks effectively as desired’ describes the variance of an actual transform with that specified by a product goal. It enables all possible outcomes of an application to be equated and evaluated. Such transforms may become the object of engineering design and so research.

1.7 Engineering Application as: performing tasks effectively, as desired.

The transformation of an object, associated with a product goal, involves many attribute state changes – both within and across levels of complexity. Consequently, there may be alternative transforms, which satisfy a product goal – website pages with different styles. The concept of ‘performing tasks effectively, as desired’ describes the variance of an actual transform with that specified by a product goal.

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1.8 Engineering Application and the User

Description of the engineering application then, is of objects, characterised by their attributes, and exhibiting an affordance, arising from the potential changes of state of those attributes. By specifying product goals, organisations express their requirement for transforms – objects with specific attribute states. Transforms are produced by ‘performing tasks effectively, as desired’, which occurs only by means of objects, affording transformation and interactive systems, capable of producing a transformation. Such production may be (part of) a engineering design.

From product goals is derived a structure of related task goals, which can be assigned either to the user or to the interactive computer (or both) within the design of an associated interactive system. The task goals assigned to the user are those, which motivate the user’s behaviours. The actual state changes (and therein transforms), which those behaviours produce, may or may not be those specified by task and product goals, a difference expressed by the concept ‘as desired’, characterised in terms of: wanted/needed/experienced/felt/valued.

2.Engineering Interactive Computers and the Human

2.1 Interactive Systems

An interactive system can be described as a behavioural system, distinguished by a boundary enclosing all human and interactive computer behaviours, whose purpose is to achieve and satisfy a common goal. For example, the behaviours of a webmaster, using a website application, whose purpose is to construct websites, constitute an interactive system. Critically, it is only by identifying the common goal, that the boundary of the interactive system can be established and so designed and researched.

Users are able to conceptualise goals and their corresponding behaviours are said to be intentional (or purposeful). Interactive computers are designed to achieve goals and their corresponding behaviours are said to be intended (or purposive). An interactive system can be described as a behavioural system, distinguished by a boundary enclosing all user and interactive computer behaviours, whose purpose is to achieve and satisfy a common goal. For example, the behaviours of a website secretary and a web application, whose purpose is to manage the site, constitute an interactive system. Critically, it is only by identifying the common goal, that the boundary of an interactive system can be established and so designed and researched.

Interactive systems transform objects by producing state changes in the abstract and physical attributes of those objects (see 1.1). The webmaster and the website application may transform the object ‘page’ by changing both the attributes of its meaning and the attributes of its layout, both text and images.

The behaviours of the user and the interactive computer are described as behavioural sub-systems of the interactive system – sub-systems, which interact. The human behavioural sub-system is more specifically termed the user. Behaviour may be loosely understood as ‘what the user does’, in contrast with ‘what is done’ (that is, attribute state changes of application objects). More precisely the user is described as:

a system of distinct and related user behaviours, identifiable as the sequence of states of a user interacting with a computer to perform tasks effectively, as desired and corresponding with a purposeful (intentional) transformation of application objects.

Although expressible at many levels of description, the user must at least be described at a level, commensurate with the level of description of the transformation of application objects. For example, a webmaster interacting with a website application is a user, whose behaviours include receiving and replying to messages, sent to the website.

2.2 Humans as a System of Mental and Physical Behaviours

The behaviours, constituting an interactive system, are both physical and abstract. Abstract behaviours are generally the acquisition, storage, and transformation of information. They represent and process information, at least concerning: application objects and their attributes, attribute relations and attribute states and the transformations, required by goals. Physical behaviours are related to, and express, abstract behaviours.

Accordingly, the user is described as a system of both mental (abstract) and overt (physical) behaviours, which extend a mutual influence – they are related. In particular, they are related within an assumed hierarchy of behaviour types (and their control), wherein mental behaviours generally determine and are expressed by, overt behaviours. Mental behaviours may transform (abstract) application objects, represented in cognition or express, through overt behaviour, plans for transforming application objects.

For example, a webmaster has the product goal, required to maintain the circulation of a website newsletter to a target audience. The webmaster interacts with the computer by means of the user interface (whose behaviours include the transmission of information in the newsletter). Hence, the webmaster acquires a representation of the current circulation by collating the information displayed by the computer screen and assessing it by comparison with the conditions, specified by the product goal. The webmaster reasons about the attribute state changes, necessary to eliminate any discrepancy between current and desired conditions of the process, that is, the set of related changes, which will produce and circulate the newsletter, ‘as desired’. That decision is expressed in the set of instructions issued to the interactive computer through overt behaviour – selecting menu options, for example.

The user is described as having cognitive, conative and affective aspects. The cognitive aspects are those of knowing, reasoning and remembering; the conative aspects are those of acting, trying and persevering; and the affective aspects are those of being patient, caring and assuring. Both mental and overt user behaviours are described as having these three aspects, all of which may contribute to ‘performing tasks effectively, as desired as wanted/needed/experienced/felt/valued.

2.3 Human-Computer Interaction

Although user and interactive computer behaviours may be described as separable sub-systems of the interactive system, these sub-systems exert a ‘mutual influence’, that is to say they interact. Their configuration principally determines the interactive system and so its design and the associated research into that and other possible engineering designs.

Interaction of the user and the interactive computer behaviours is the fundamental determinant of the interactive system, rather than their individual behaviours per se. Interaction is described as: the mutual influence of the user (i.e. behaviours) and the interactive computer (i.e behaviours), associated within an interactive system. For example, the behaviours of a webmaster interact with the behaviours of a website application. The webmaster’s behaviours influence the behaviours of the interactive computer (access the image function), while the behaviours of the interactive computer influence the selection behaviour of the webmaster (among possible image types). The design of their interaction – the webmaster’s selection of the image function, the computer’s presentation of possible image types – determines the interactive system, comprising the webmaster and interactive computer behaviours in their planning and control of webpage creation. The interaction may be the object of engineering design and so design research.

The assignment of task goals by design then, to either the user or the interactive computer, delimits the former and therein specifies the design of the interaction. For example, replacement of an inappropriate image, required on a page is a product goal, which can be expressed as a task goal structure of necessary and related attribute state changes. In particular, the field for the appropriate image as an attribute state change in the spacing of the page. Specifying that state change may be a task goal assigned to the user, as in interaction with the behaviours of early image editor designs or it may be a task goal assigned to the interactive computer, as in interaction with the GUI ‘fill-in’ behaviours. Engineering design research would be expected to have contributed to the latter . The assignment of the task goal of specification constitutes the design of the interaction of the user and interactive computer behaviours in each case, which in turn may become the object of research.

2.4 Human On-line and Off-line Behaviours

User behaviours may comprise both on-line and off-line behaviours: on-line behaviours are associated with the interactive computer’s representation of the application; off-line behaviours are associated with non-computer representations of the application.

As an illustration of the distinction, consider the example of an interactive system, consisting of the behaviours of a website secretary and an e-mail application. They are required to produce a paper-based copy of a dictated letter, stored on audio tape. The product goal of the interactive system here requires the transformation of the physical representation of the letter from one medium to another, that is, from tape to paper. From the product goal derives the task goals, relating to required attribute state changes of the letter. Certain of those task goals will be assigned to the secretary. The secretary’s off-line behaviours include listening to and assimilating the dictated letter, so acquiring a representation of the application object. By contrast, the secretary’s on-line behaviours include specifying the represention by the interactive computer of the transposed content of the letter in a desired visual/verbal format of stored physical symbols.

On-line and off-line user behaviours are a particular case of the ‘internal’ interactions between a user’s behaviours as, for example, when the web secretary’s keying interacts with memorisations of successive segments of the dictated letter.

2.5 Structures and the Human

Description of the user as a system of behaviours needs to be extended, for the purposes of design and design research, to the structures supporting that behaviour.

Whereas user behaviours may be loosely understood as ‘what the human does’, the structures supporting them can be understood as ‘the support for the human to be able to do what they do’. There is a one-to-many mapping between a user’s structures and the behaviours they might support: thus, the same structures may support many different behaviours.

In co-extensively enabling behaviours at each level of description, structures must exist at commensurate levels. The user structural architecture is both physical and mental, providing the capability for a user’s overt and mental behaviours. It provides a represention of application information as symbols (physical and abstract) and concepts, and the processes available for the transformation of those representations. It provides an abstract structure for expressing information as mental behaviour. It provides a physical structure for expressing information as physical behaviour.

Physical user structure is neural, bio-mechanical and physiological. Mental structure consists of representational schemes and processes. Corresponding with the behaviours it supports and enables, user structure has cognitive, conative and affective aspects. The cognitive aspects of user structures include information and knowledge – that is, symbolic and conceptual representations – of the application, of the interactive computer and of the user themselves, and it includes the ability to reason. The conative aspects of user structures motivate the implementation of behaviour and its perseverence in pursuing task goals. The affective aspects of user structures include the personality and temperament, which respond to and support behaviour. All three aspects may contribute to ‘ performing tasks effectively, as desired as wanted/needed/experienced/felt/valued’.

To illustrate this description of mental structure, consider the example of the structures supporting a web user’s behaviours. Physical structure supports perception of the web page display and executing actions to the web application. Mental structures support the acquisition, memorisation and transformation of information about how the web application is conducted. The knowledge, which the web user has of the application and of the interactive computer, supports the collation, assessment and reasoning about the actions required.

The limits of user structures determine the limits of the behaviours they might support. Such structural limits include those of: intellectual ability; knowledge of the application and the interactive computer; memory and attentional capacities; patience; perseverence; dexterity; and visual acuity etc. The structural limits on behaviour may become particularly apparent, when one part of the structure (a channel capacity, perhaps) is required to support concurrent behaviours, perhaps simultaneous visual attending and reasoning behaviours. The user then, is ‘resource-limited’ by the co-extensive user structures.

The behavioural limits of the user, determined by structure, are not only difficult to define with any kind of completeness, they may also be variable, because that structure may change, and in a number of ways. A user may have self-determined changes in response to the application – as expressed in learning phenomena, acquiring new knowledge of the application, of the interactive computer, and indeed of themselves, to better support behaviour. Also, user structures degrade with the expenditure of resources by behaviour, as demonstrated by the phenomena of mental and physical fatigue. User structures may also change in response to motivating or de-motivating influences of the organisation, which maintains the interactive system.

It must be emphasised that the structure supporting the user is independent of the structure supporting the interactive computer behaviours. Neither structure can make any incursion into the other and neither can directly support the behaviours of the other. (Indeed this separability of structures is a pre-condition for expressing the interactive system as two interacting behavioural sub-systems). Although the structures may change in response to each other, they are not, unlike the behaviours they support, interactive; they are not included within the interactive system. The combination of structures of both user and interactive computer, supporting their interacting behaviours is described as the user interface .

2.6 Human Resource Costs

‘Performing tasks effectively as desired’ by means of an interactive system always incurs resource costs. Given the separability of the user and the interactive computer behaviours, certain resource costs are associated directly with the user and distinguished as structural user costs and behavioural user costs.

Structural user costs are the costs of the user structures. Such costs are incurred in developing and maintaining user skills and knowledge. More specifically, structural user costs are incurred in training and educating users, so developing in them the structures, which will enable the behaviours necessary for an application . Training and educating may augment or modify existing structures, provide the user with entirely novel structures, or perhaps even reduce existing structures. Structural user costs will be incurred in each case and will frequently be borne by the organisation. An example of structural user costs might be the costs of training a secretary to use a GUI web interface in the particular style of layout, required for an organisation’s correspondence with its clients and in the operation of the interactive computer by which that layout style can be created.

Structural user costs may be differentiated as cognitive, conative and affective structural costs. Cognitive structural costs express the costs of developing the knowledge and reasoning abilities of users and their ability for formulating and expressing novel plans in their overt behaviour – as necessary for ‘performing tasks effectively, as desired’. Conative structural costs express the costs of developing the activity, stamina and persistence of users as necessary for an application. Affective structural costs express the costs of developing in users their patience, care and assurance as necessary for an application.

Behavioural user costs are the resource costs, incurred by the user (i.e by the implementation of their of behaviours) in recruiting user structures to effect an application. They are both physical and mental resource costs. Physical behavioural costs are the costs of physical behaviours, for example, the costs of making keystrokes on a keyboard and of attending to a web screen display; they may be expressed without differentiation as physical workload. Mental behavioural costs are the costs of mental behaviours, for example, the costs of knowing, reasoning, and deciding; they may be expressed without differentiation as mental workload. Mental behavioural costs are ultimately manifest as physical behavioural costs. Costs are an important aspect of the engineering design of an interactive computer system.

When differentiated, mental and physical behavioural costs are described as the cognitive, conative and affective behavioural costs of the user. Cognitive behavioural costs relate to both the mental representing and processing of information and the demands made on the user’s extant knowledge, as well as the physical expression thereof in the formulation and expression of a novel plan. Conative behavioural costs relate to the repeated mental and physical actions and effort, required by the formulation and expression of the novel plan. Affective behavioural costs relate to the emotional aspects of the mental and physical behaviours, required in the formulation and expression of the novel plan. Behavioural user costs are evidenced in user fatigue, stress and frustration; they are costs borne directly by the user and so need to be taken into account in the engineering design process.

3. Performance of the Engineering Interactive Computer System and the User.

‘To perform tasks effectively, as desired’ derives from the relationship of an interactive system with its application. It assimilates both how well the application is performed by the interactive system and the costs incurred by it. These are the primary constituents of ‘performing tasks effectively, as desired’, that is performance. They can be further differentiated, for example, as wanted/needed/experienced/felt/valued.

A concordance is assumed between the behaviours of an interactive system and its performance: behaviours determine performance. How well an application is performed by an interactive system is described as the actual transformation of application objects with regard to the transformation, demanded by product goals. The costs of carrying out an application are described as the resource costs, incurred by the interactive system and are separately attributed to the user and the interactive computer. Specifically, the resource costs incurred by the user are differentiated as: structural user costs – the costs of establishing and maintaining the structures supporting behaviour; and behavioural user costs – the costs of the behaviour, recruiting structure to its own support. Structural and behavioural user costs are further differentiated as cognitive, conative and affective costs. Design requires attention to all types of resource costs – both those of the user and of the interactive computer.

‘Performing tasks effectively, as desired’ by means of an interactive system may be described as absolute or as relative, as in a comparison to be matched or improved upon. Accordingly, criteria expressing ‘as desired’ may either specify categorical gross resource costs and how well an application is performed or they may specify critical instances of those factors to be matched or improved upon. They are the object of engineering design and so of design research.

Discriminating the user’s performance within the performance of the interactive system would require the separate assimilation of user resource costs and their achievement of desired attribute state changes, demanded by their assigned task goals. Further assertions concerning the user arise from the description of interactive system performance. First, the description of performance is able to distinguish the goodness of the transforms from the resource costs of the interactive system, which produce them. This distinction is essential for engineering design, as two interactive systems might be capable of producing the same transform, yet if one were to incur a greater resource cost than the other, it would be the lesser (in terms of performance) of the two systems.

Second, given the concordance of behaviour with ‘performing tasks effectively, as desired’, optimal user (and equally, interactive computer) behaviours may be described as those, which incur a (desired) minimum of resource costs in producing a given transform. engineering design of optimal user behaviour would minimise the resource costs, incurred in producing a transform of a given goodness. However, that optimality may only be categorically determined with regard to interactive system performance and the best performance of an interactive system may still be at variance with what is desired of it. To be more specific, it is not sufficient for user behaviours simply to be error-free. Although the elimination of errorful user behaviours may contribute to the best application possible of a given interactive system, that performance may still be less than ‘as desired’. Conversely, although user behaviours may be errorful, an interactive system may still support ‘performing tasks effectively, as desired’.

Third, the common measures of human ‘performance’ – errors and time, are related in this conceptualisation of performance. Errors are behaviours, which increase resource costs, incurred in producing a given transform or which reduce the goodness of the transform or both. The duration of user behaviours may (very generally) be associated with increases in behavioural user costs.

Fourth, structural and behavioural user costs may be traded-off in the design of an application. More sophisticated user structures, supporting user behaviours, that is, the knowledge and skills of experienced and trained users, will incur high (structural) costs to develop, but enable more efficient behaviours – and therein, reduced behavioural costs.

Fifth, resource costs, incurred by the user and the interactive computer may be traded-off in the design of the performance of an application. A user can sustain a level of performance of the interactive system by optimising behaviours to compensate for the poorly designed behaviours of the interactive computer (and vice versa), that is, behavioural costs of the user and interactive computer are traded-off in the design process. This is of particular importance as the ability of users to adapt their behaviours to compensate for the poor design of interactive computer-based systems often obscures the fact that the systems are poorly designed.

Requirement 1: The framework (as a basic support structure) is for a discipline (as an academic field of study and branch of knowledge).

Newman is concerned with the discipline of Software Engineering (Comment 1), of which HCI is treated as being a part (Comment 3). Software Engineering, in turn, is considered to be an Engineering Design Discipline and so by implication an academic field of study and a branch of knowledge.

Requirement 2: The framework is for HCI (as human-computer interaction) as engineering (as design for performance).

The paper references performance, expressed both as errors (Comment 11) and time (Comment 12)

Requirement 3: The framework has a general problem (as engineering design) with a particular scope (as human computer interactions to perform tasks effectively, as desired).

The paper espouses the concept of HCI as engineering design (Comment 3). Tasks, such as text editing, are performed as needed and required by the end-user. Such performance is expressed in terms of time (Comment 11) and time (Comment 12).

Requirement 4:  Research ( as acquisition and validation) acquires (as study and practice) and validates (as confirms) knowledge (as design guidelines/models and methods/principles – specific/ general and declarative/methodological).

The paper references the designed artefact (Comment 5) and the methods used to design it (Comments 2 and 4). This knowledge comprises empirical methods, such as testing (Comment 7) and also analytic models (Comment 9). A model is proposed linking needs to their implementation (Comment 6).

Requirement 5:  This knowledge supports (facilitates) practices (diagnose design problem and prescribe design solution), which solve (as resolve) the general design problem of engineering design.

The paper references design practices, such as implement and test (Comment 7), generate and test (Comment 6) and both analytical and empirical practices (Comments 8 and 9).

Conclusion:

Newman’s paper obviously espouses the concept of HCI, as part of Software Engineering, and so part of an engineering design discipline. The framework is more-or-less complete at a high level of description with its references to models, methods and performance. Its needs/implementation model (Figure 1) is not operationalised, however, and so the paper does not provide a case-study of the acquisition of design knowledge. To do so would require the framework to be expressed at lower levels of description, as proposed here.

First, the Framework, as a basic support structure, is for a discipline, as an academic field of study and branch of knowledge.

Potential: Blandford’s Engineering Approach conceives HCI as an Engineering discipline, for which she offers two alternative high-level views. No other discipline is referenced.

Second, the Framework is for HCI, as human-computer interaction, as Engineering, that is, as design for performance.

Potential: Blandford’s Engineering Approach offers two views of design and implicitly references performance in terms of: usability; utility and experience. No details, concerning the latter, are offered with respect to their relationship with the former.

Third, the Framework has a general problem, as engineering design, with a particular scope, as engineering human computer interactions to perform tasks effectively as desired.

Potential: Blandford’s Engineering Approach implicitly references user needs with ‘as desired’ and effectiveness in terms of: usability; utility and experience. No details are offered for either reference.

Fourth, the Framework supports research, as acquisition and validation, which acquires, as study and practice and validates, as confirms, knowledge, that is design guidelines/models and methods/principles both specific/ general and declarative/methodological.

Potential: Blandford’s Engineering Approach references validation, in terms of: usability; utility and experience. No details, however, are provided concerning design knowledge.

Fifth, the Framework embodies knowledge, which supports, as facilitates practices, as diagnose design problem and prescribe design solution, which solve, as resolve, the general design problem of engineering design.

Potential: Blandford’s Engineering Approach does not address the issue of knowledge or its relationship to the contrastive design practises of the two views of Engineering, which she offers.

Conclusion:Blandford’s Engineering Approach to HCI research is expressed at a very general level, commensurate with the questioning nature of her paper. However, the Approach could be further developed with respect to: the relationship between performance and usability, utility and experience; likewise for effectiveness, validation and HCI design knowledge.

The Engineering Framework proposed here is considered to have potential for contributing to such developments.

Discipline

Innovation – an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

Art – an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

Craft – an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

Applied – an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

Science – Discipline: an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

Engineering – an academic field of study/branch of knowledge (academic – scholarly; field of study – subject area; branch of knowledge – division of information/learning).

HCI

Innovation – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Art – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Craft – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Applied – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Science – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Engineering – human-computer interaction (human – individual/group; computer – interactive/embedded; interaction – active/passive).

Framework Type

Innovation – Innovation: novel (novel – new ideas/methods/devices etc)

Art – Art: creative expression corresponding to some ideal or criteria (creative – imaginative, inventive); (expressive – showing by taking some form); ideal – visionary/perfect); criterion – standard).

Craft – Craft: best practice design (practice – design/evaluation; design – specification/implementation).

Applied – Applied: application of other discipline knowledge (application – addition to/prescription; discipline – academic field/branch of knowledge; knowledge – information/learning).

Science – understanding (explanation/prediction)

Engineering – design for performance (design – specification/implementation; performance – how well effected).

General Problem

Innovation – innovation design (innovation – novelty; design – specification/implementation).

Art – art design (art – ideal creative expression; design – specification/implementation).

Craft – craft design (craft – best practice; design – specification/implementation).

Applied – applied design (applied – added/prescribed; design – specification/implementation).

Science – understanding human-computer interactions (understand – explanation/prediction; human – individual/group; computer – interactive/embedded; interaction – active/passive)

Engineering – engineering design (engineering – design for performance; design – specification/implementation).

Particular Scope

Innovation – innovative human-computer interactions to do something as desired (innovative – novel; human – individual/group; computer – interactive/embedded; interactions – active/passive; something – action/task; desired: wanted/needed/experienced/felt/valued).

Art – art human-computer interactions to do something as desired (art – creation/expression; human – individual/group; computer – interactive/embedded; interactions – active/passive; something – action/task); desired: wanted/needed/experienced/felt/valued).

Craft – human-computer interactions to do something as desired, which satisfy user requirements in the form of an interactive system (human – individual/group; computer – interactive/embedded; interactions – active/passive; something – action/task; desired: wanted/needed/experienced/felt/valued; user – human; requirements – needs; satisfied – met/addressed; interactive – active/passive; system – user-computer).

Applied – human-computer interactions to do something as desired, which satisfy user requirements in the form of an interactive system (human – individual/group; computer – interactive/embedded; interactions – active/passive; something – action/task; desired: wanted/needed/experienced/felt/valued; user – human; requirements – needs; satisfied – met/addressed; interactive – active/passive; system – user-computer).

Science – human-computer interactions to do something as desired (human – individual/group; computer – interactive/embedded; interactions – active/passive; something – action/task; desired: wanted/needed/experienced/felt/valued.

Engineering – human-computer interactions to perform tasks effectively as desired (human – individual/group; computer – interactive/embedded; interactions – active/passive; perform – effect/carry out; tasks – actions; desired – wanted/needed/experienced/felt/valued).

Research

Innovation – acquires and validates knowledge to support practices (acquires – creates; validates – confirms; knowledge – patents/expert advice/experience/examples).

Art – acquires and validates knowledge (acquires – creates by study/practice; validates – confirms; knowledge – experience/expert advice/other artefacts.

Craft – acquires and validates knowledge to support practices (acquires – creates; validates – confirms; knowledge – heuristics/methods/expert advice/successful designs/case-studies).

Applied – acquires and validates knowledge to support practices (acquires – creates; validates – confirms; knowledge – heuristics/methods/expert advice/successful designs/case-studies).

Science – acquires and validates knowledge to support practices (acquires – creates; validates – confirms; knowledge – theories/models/laws/data/hypotheses/analytical and empirical methods and tools; practices – explanation/prediction).

Engineering – acquires and validates knowledge to support practices (acquires – creates; validates – confirms; knowledge – design guidelines/models and methods/principles – specific/ general and declarative/methodological).

Knowledge

Innovation – supports practices (supports – facilitates/makes possible; practices – trial-and-error/implement and test).

Art – supports practices (supports – facilitates/makes possible; practices – trial and error/implement and test).

Craft – supports practices (supports – facilitates/makes possible; practices – trial-and-error/implement and test).

Applied – supports practices (supports – facilitates/makes possible; practices – trial-and-error/apply and test).

Science – supports practices (supports – facilitates/makes possible; practices – explanation/prediction).

Engineering – supports practices (supports – facilitates/makes possible; practices – diagnose design problems/prescribe design solutions).

Practices

Innovation – supported by knowledge (supported – facilitated; knowledge – patents/expert advice/experience/examples).

Art – supported by knowledge (supported – facilitated/made possible; knowledge – experience/expert advice/other artefacts).

Craft – supported by knowledge (supported – facilitated; knowledge – heuristics/methods/expert advice/successful designs/case-studies).

Applied – supported by knowledge (supported – facilitated; knowledge – guidelines; heuristics/methods/expert advice/successful designs/case-studies).

Science – supported by knowledge (supported – facilitated; knowledge – theories/models/laws/data/hypotheses/analytical and empirical methods and tools ).

Engineering – supported by knowledge (supported – facilitated; knowledge – design guidelines/models and methods/principles – specific/ general and declarative/methodological).

Solution

Innovation – resolution of a problem (resolution – answer/address; problem – question/doubt).

Art – resolution of the general problem (resolution – answer/address; problem – question/doubt).

Craft – resolution of a problem (resolution – answer/address; problem – question/doubt).

Applied – resolution of a problem (resolution – answer/address; problem – question/doubt).

Science – resolution of a problem (resolution – answer/address; problem – question/doubt).

Engineering – resolution of a problem (resolution – answer/address; problem – question/doubt).