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Design and use as plans: An action-theoretical account
Article in Design Studies · May 2002
DOI: 10.1016/S0142-694X(01)00040-0
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Submitted to Design Studies
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revised: August 21, 2001
Design and use as plans:
an action-theoretical account
Wybo Houkes, Department of Philosophy, Delft University of Technology, Jaffalaan 5, NL2628 BX Delft, The Netherlands,
Pieter E. Vermaas, Department of Philosophy, Delft University of Technology, Jaffalaan 5,
NL-2628 BX Delft, The Netherlands,
Kees Dorst, Faculty of Industrial Design Engineering, Delft University of Technology,
Jaffalaan 9, NL-2628 BX Delft, The Netherlands,
Marc J. de Vries, Faculty of Technology Management, Eindhoven University of Technology,
P.O. Box 513, NL-5600 MB Eindhoven, The Netherlands.
In this paper, we present an action-theoretical account of use and design. Central to this
account is the notion of a user plan, which leads us to distinguish a cycle of plan design from
one of artefact design. We comment on the nature and scope of our account from the
perspective of design methodology in general, and we show that it can be employed to analyse
the shortcomings of one design method in particular, namely quality function deployment.
Finally, we examine some consequences for a philosophy of artefacts and their function.
Keywords: philosophy of design, action theory, user plan, quality function deployment
‘Philosophy of design’ can be interpreted in many ways, but it surely includes philosophy of
intentional action. Indeed, the few references to design in philosophy, e.g., in the context of
the so-called ‘argument from design’ for the existence of God, regard it as a paradigm of such
action. Therefore, in this paper, we will present an action-theoretical framework for design.
Most philosophy of design has the structure of comparing its subject with another
phenomenon that is more commonly studied by philosophers. This is a valuable approach,
because it draws on the wealth of theories and concepts in, for instance, philosophy of science
or epistemology. Yet exclusively drawing up similarities and differences between design and
other phenomena may overlook features that make design interesting in its own right.
Therefore, in this paper, which is a collaboration of philosophers and design methodologists,
we seek a more independent approach to design. Our point of departure is the plain fact that
design is a type of action. We therefore present an action-theoretical framework,
reconstructing design in terms of plans, intentions, and what philosophers call ‘practical
reasoning’.
But before focussing on design itself, we shall study a related and equally neglected activity,
namely use. The action-theoretical framework for use presented in Section 1 accords a central
role to user plans. This is used as input for the framework of design (Section 2), which is
divided into a ‘plan-design’ part and an ‘artefact-design’ part. Having presented our
frameworks of design and use, linked by a user plan, we connect it to design methodology.
First of all, we comment on its value and scope from a design methodologist’s point of view
(Section 3), and then we put it to use in analysing a specific method: quality function
deployment. It will turn out that some shortcomings of this method can be phrased in terms of
our model (Section 4). Finally, we study the consequences of our framework for the
philosophy of artefacts and their functions (Section 5).
1
An action-theoretical framework for use
Action theory is a branch of philosophy that studies the formal structure and explanation of
human action. It reflects ordinary usage of the term ‘action’ by describing it in such terms as
‘means’, ‘ends’, ‘plans’, and ‘intentions’. On the other hand, action theory introduces new
terminology, such as ‘practical reasoning’. In our account, we shall mainly use ‘intention’ and
‘plan’, and implicitly invoke practical reasoning:
•
•
•
Intentions are usually characterised in philosophy as requiring a combination of
desires and beliefs: one intends to do something if and only if one wants to do it and
believes that one has a chance of achieving it. 1
Plans are orderings of considered actions, undertaken for achieving a goal. 2 These
orderings may be linear, determining the exact order in which actions are taken (‘I’ll
do this, then that’), or partial, including multiple options (‘If this obtains, I’ll do that;
otherwise, I’ll do something else’). Furthermore, plans are subject to certain standards
of rationality. 3 For instance: the goals included must be realisable at the same time and
the planning agent must only rely on beliefs he holds to be true. The plan should also
be means-end coherent: the means chosen must be considered appropriate (i.e.,
necessary, sufficient, or optimal) to the goals. 4 These standards introduce normativity,
criteria for assessing whether a plan is good / rational or bad / irrational.
Practical reasoning is the process by which an agent forms intentions and plans, based
on desires and beliefs. We shall assume that every intention and subsequent action can
be reconstructed as being based on practical reasoning, even if there is no sequence of
explicit decisions and belief-formations in the agent’s mind. 5
In this section and the next, we shall reconstruct use and design as plans based on practical
reasoning. This approach is somewhat biased. For one thing, it paints a picture of use and
design as primarily intellectual processes: although plans lead to action, actually doing what is
planned is not regarded as an important step in its own right (intentions may or may not lead
to action, but this is irrelevant to the structure of the plan). Our approach shares this
1
Davidson D Replies to Essays I-IX in B Vermazen and M Hintikka (eds) Essays on Davidson: Action and
Events Clarendon Press, Oxford (1985). The literature on action theory contains many objections and
alternatives to Davidson’s view, but it is perhaps the closest thing to a received view in the field.
2
Audi R Intention, Cognitive Commitment, and Planning Synthese Vol 86 (1991) pp 361-378
3
Bratman M Intentions, Plans and Practical Reason Harvard University Press, Cambridge, MA (1987)
4
These criteria, and many others, are developed in Audi R Practical Reasoning Routledge, London (1989)
chapter 7
5
This ‘inferentialist’ view is defended in Audi (1989) pp 113-119
2
intellectualist bias with action theory itself, which is, perhaps surprisingly, more concerned
with deliberation than with action. Nonetheless, we believe that applying this philosophical
discipline to use and design brings out central features of these activities.
So let us start by presenting an action-theoretical account of the use of objects (see figure 1
for a schematic representation):
U.1
U.2
U.3
U.4
U.5
U.6
U.7
The user intends to bring about some state of affairs φ, because he wants φ and
believes it does not obtain.
The user believes that carrying out an appropriate user plan P that involves the use
of objects O1, O2, etc., will bring about φ.
The user believes that the physical circumstances support carrying out P.
The user believes that he possesses the skills needed for carrying out P.
(from steps 1, 2, 3 and 4, by practical reasoning) The user intends to carry out P and
acts accordingly.
The user believes that φ has been brought about or that it has not been brought about,
based on the observation of φ′ as the outcome of P and a comparison of φ′ with φ.
(from steps 1 and 6) The user believes that φ has been achieved or not. In the latter
case, he may decide to repeat cycle U and to reconsider his intended state of affairs
φ, to select another user plan P′, or both.
For example: I intend to clean my car (U.1). I believe that rubbing the car with a sponge
soaked in water and soap will contribute to this aim (U.2), that it is not freezing outside (U.3)
and that I am skilled at handling a sponge (U.4); therefore, I intend to rub the car with a
sponge soaked in water and soap (U.5). After rubbing it with the sponge, I observe the present
state of my car and decide whether I think it is clean enough (U.6). Finally, I decide to give it
a second rinse, to go to the washing lane after all, or to go inside and read a book (U.7).
Goal:
state of affairs φ
Means:
plan P
Action:
carrying out P
Comparison:
φ with result φ′
Evaluation:
is φ achieved?
yes
no
3
Figure 1. Visualisation of use; the arrows indicate the temporal order of the different actions.
Step U.2 is crucial to the rationality of the cycle as a whole, for in this step, the user decides
on the method and means for realising his goal. As characterised above, rational plans are at
least means-end coherent. 6 Therefore it is included that the agent should believe that the user
plan P that he selects to realise his aims is appropriate. There appear to be three, often
overlapping, grounds for this belief:
Physical properties: The user believes that P is appropriate because of his beliefs about
relevant physical properties and dispositions of O1, O2, etc.
Fellow users: The user believes that P is appropriate because he has been shown or told by
others that P may be carried out in order to bring about states of affairs similar to φ.
Designers: The user believes that P is appropriate because he believes that P and perhaps
some of the objects O1, O2, etc. have been designed for bringing about states of affairs
similar to φ.
In the car-washing example, I may plan to wash my car with a sponge, because I believe it has
a soft and absorbent physical structure, because I have seen others use a sponge and decide to
use one myself, or because the sponge has ‘For washing cars, windows, etc.’ written on the
package.
In the latter case, the appropriateness of carrying out a user plan P involving an object O may,
if object O is designed, be expressed by saying that O is an artefact with the function of
bringing about this state of affairs. This artefact is, by our definition, included in a user plan
P. Although rather straightforward in the case of a sponge, in other cases, this user plan may
plausibly be said to be designed along with the artefacts involved.
2
An action-theoretical framework for design
In the previous section, we introduced the idea of design of user plans and artefacts. In this
section, we shall develop this idea by reconstructing the design process in terms of plans,
intentions, and practical reasoning. Central to this reconstruction are two nested plans, PD and
AD, which represent the design of a user plan and of artefacts respectively.
The plan-design cycle PD has the following structure (see figure 2 for a schematic
representation):
PD.1
PD.2
PD.3
PD.4
The designer wants to contribute to his clients’ goal of bringing about a state of
affairs φ.
The designer believes that φ′, satisfying requirements R, is the closest consistent and
viable approximation of φ.
(from steps 1 and 2 by the characterisation of intention) The designer intends to
contribute to bringing about a state of affairs φ′.
The designer believes that a considered user who is following an appropriate user
plan P that involves the use of objects O1, O2, etc., and of artefact A1 with functions
Note that there are now two plans in play: the user plan P and the cycle U itself. We advance that the cycle U is
means-end coherent only if the user believes that the chosen user plan P is appropriate to the goal φ.
6
4
PD.5
PD.6
PD.7
PD.8
PD.9
PD.10
f1, g1, …, satisfying requirements R1, artefact A2 with functions f2, g2, …, satisfying
requirements R2, etc., will contribute to bringing about φ′. 7
(from steps 3 and 4 by practical reasoning) The designer intends to construct a user
plan P and to communicate it to the considered users.
(from step 5 by inclusion) The designer intends to contribute to producing artefact
A1 with functions f1, g1, …, satisfying requirements R1, artefact A2 with functions f2,
g2, …, satisfying requirements R2, etc., by designing 8 each artefact by means of a
design cycle AD, and acts accordingly.
The designer checks whether the resulting designs of A1, A2, etc., are consistent with
P, and returns to either step 4 or 5 if this is not the case.
The designer decides to communicate P to the considered users, and acts
accordingly.
The designer believes that φ′ can or cannot be brought about by considered users to
whom P is communicated. This belief is based on the observation that some of these
users go through a sequence of actions P′ and bring about φ′′, and on a comparison
of φ′′ with φ′.
The designer decides that his goal to contribute to bringing about φ′ has been
achieved or not. In the latter case, he may decide to repeat the entire cycle PD, settle
on another plan (return to step 4), repeat at least one design cycle AD (return to step
6) or re-attempt communication (return to step 8).
This belief is based on beliefs about the appropriateness of the means to the considered user’s goal, about the
physical circumstances of considered use, and about the skills of the considered user. The latter beliefs
correspond to steps U.2 to U.4 of cycle U. In practice, the designer may gradually devise user plan P by
formulating a tentative plan, checking data on consumer behaviour, reformulating the plan, etc. For brevity’s
sake, we omitted this part of the designer’s practical reasoning in our reconstruction.
8
‘Designing’ is here used in the broad sense of describing the artefacts in words, pictures, gestures or some
combination of these, along with instructions for producing the artefacts.
7
5
Goal:
contribute to client’s goal
Means:
plan P with A1, A2, …, to
realise state of affairs φ′
Action:
constructing plan P
and
designing A1, A2, … by AD
and
communicating P to users
Comparison:
φ′ with result φ′′ obtained
by users familiar with P
does P enable users to
achieve φ′?
Evaluation:
yes
no
Figure 2. Visualisation of plan design.
In this cycle, we left aside the reasons for the designer’s choice of an alternative state of
affairs φ′, which may, by the way, be identical to φ, and a set of artefacts A1, A2, etc. One of
the sources of φ′ is, of course, the set of requirements R, which may not all be included in the
clients’ goal; they may include, among other things, government regulations and the
designer’s wish for safe and durable artefacts. And the designer’s past experience is clearly an
important reason for his choice of artefacts A1, A2, etc. But, in actual practice, the choices of
φ′ and A1, A2, etc. will be interdependent as well. In some cases, the choice of φ′ may even be
dictated by the artefacts that the designer has experience with or easy access to. If the model
of the design process developed in this section is correct, this primacy of artefacts over plans
may lead to the presupposition of an inappropriate user plan and thus to unsuccessful designs.
For, in the PD cycle given above, the design of artefacts is a step or phase of the plan-design
cycle, being part of PD.6. This phase of artefact design has an action-theoretical structure of
its own (see figure 3 for a schematic representation):
AD.1
AD.2
The designer intends to bring about a state of affairs δ, i.e., the existence of a design
of an artefact A with functions f, g, etc., that satisfies requirements R.
The designer believes that describing an object 9 O is an appropriate means to
bringing about δ.
The term ‘object’ may refer to a particular material item, a type of material items, an abstract item, etc. Since
the goal of our paper is to give an action-theoretical account of design rather than study its ontological
9
6
AD.3
AD.4
AD.5
AD.6
(from steps 1 and 2 by practical reasoning) The designer intends to describe O, and
acts accordingly.
The designer decides, if appropriate, 10 to construct a specimen of O (a prototype, a
sample, a pilot model), and acts accordingly.
The designer believes that δ has been brought about or has not been brought about,
based on his observation of δ′ (the existence of a design of an artefact A with
function f′ that satisfies requirements R′) as the outcome of his actions, and on a
comparison of δ′ with δ.
(from steps 1 and 5) The designer decides that his goal has been achieved (f′ is equal
to f and R′ include the original requirements R) or not. In the former case, he
proceeds to step PD.7. In the latter case, he may decide to repeat AD and to change
the intended state of affairs δ, to select another description of O, or both.
The rationality of this cycle depends, among other things, on the grounds the designer has for
choosing a specific description of an object O as a means to δ in step AD.2. Again, the
standards for rationality include means-end coherence, i.e., grounds for believing that the
means are appropriate.
A simple construal of these grounds is that the designer has certain beliefs about object O as a
physical object with structure S. If, for instance, the artefact has the function to stabilise a
ship, the designer may choose to describe pieces of rock with specific shapes, sizes and
weights. Another simple construal is that the designer believes that the description of some
already existing artefact A′ with function f′, g′, etc., will be appropriate to designing A. If, for
instance, A has the function of conducting an electrical current, designers usually choose from
existing wires. But in general AD.2 will be more complicated. Designers typically decompose
into sub-functions the functions of A and try to design components with those sub-functions.
In this way, artefact design becomes recursive. As a general reconstruction of step AD.2 we
therefore propose the following. The designer chooses one of the options a, b or c, given by:
The designer decides to describe a physical object O with structure S, possibly
including instructions for processing and shaping it.
AD.2.b
The designer decides to describe an existing artefact A′ with functions f′, g′, etc.
AD.2.c.1 The designer decides to describe a composite of components O1, O2, …, where O1
has sub-functions f1, g1, …, where O2 has sub-functions f2, g2, …, etc. The designer
possibly includes instructions for assembling these components.
AD.2.c.2 The designer designs the components by reiterating cycle AD for each component
O1, O2, etc.
AD.2.c.3 The designer considers the integration of components A1, A2, etc.
AD.2.a
commitments, we leave aside the question of the nature of object O. But cf. Galle P Design as Intentional
Action: A Conceptual Analysis Design Studies 20 (1999) pp 57–81.
10
See the remarks on simulation in Section 3.
7
PD
Goal:
Means:
a design δ of artefact A
description of object O as:
an object with structure S
or
an existing artefact A′
or
a composite with
components O1, O2 …
Action:
describing O
Comparison:
description of O with δ
Evaluation:
is the description of O a
design of A?
yes
no
PD
Figure 3. Visualisation of artefact design.
Typically, designers do not immediately choose either step AD.2.a or AD.2.b (the latter would
even amount to plagiarism) but rather start by decomposition (step AD.2.c). Only after this
decomposition, the steps AD.2.a or AD.2.b are considered. The design of new materials
presents a present-day example of step AD.2.a. And the importance of step AD.2.b is nicely
illustrated by the term ‘brochure engineering’ 11 which refers to the practice of designing
installations by decomposing them (step AD.2.c for A) into components and then selecting
existing artefacts from various brochures for these components (step AD.2.b for every
component O1, O2, …).
We have left unspecified how, in step AD.2.c.1, the designer manages to decompose the
artefact A into components. Two procedures come to mind. Firstly, the designer can consider
the different functions f, g, … of A, and decide to introduce components for each of these
functions separately. So, component O1 has function f, component O2 has function g, etc.
Secondly, the designer can consider existing designs of compound artefacts that have
functions similar to those of A. The decompositions of these existing artefacts can then be
taken as templates for decomposing A. This second procedure may account for the importance
11
Private communication with C. Friederich.
8
of past experience in design practice, and for the continuous evolution of (designs of)
technical artefacts. 12
Another thing left unspecified is how the designer integrates components O1, O2, … (step
AD.2.c.3). A minimal construal is that the designer checks the validity of step AD.2.c.1, i.e.,
whether the components, when assembled, indeed constitute artefact A. Alternatively, the
designer may not only check step AD.2.c.1, but also consider whether the components O1, O2,
… fit in with the overall design of A. The difference between these two methods becomes
clear when one considers designs with multiple decomposition steps. In integrating subcomponents O11, O12, … of a component O1, the latter method compares O11, O12, … with
other components of the artefact and their sub-components, whereas the former method only
compares them with each other. In practice, this overall comparison may be made redundant
by adding (normalisation) requirements to the requirements R1, R2, … imposed on the
components.
The connection between the design cycles outlined in this section can be schematically
represented as in figure 4.
PD
AD
AD′
client’s goal
design of artefact A
plan P
with A1, A2, …
design of part O1
constructing plan P
and
designing A1, A2, …
and
communicating P
is description of O a
design of A?
is client’s goal
obtained by P?
yes
describing object O
as: structure S
or
existing artefact A′
or
composite O1+O2+⋅⋅
yes
no
Et cetera, et cetera, ...
is description of O a
design of O1?
yes
no
no
Figure 4. Visualisation of the whole design process; the arrows still indicate temporal order.
3
Connecting the framework to design methodology
Basalla G The Evolution of Technology Cambridge University Press, Cambridge (1988); Ziman J (ed)
Technological Innovation as an Evolutionary Process Cambridge University Press, Cambridge (2000)
12
9
In the preceding sections, we presented our action-theoretical framework for use and design.
We now switch perspectives and regard it from a design methodologists’ point of view. In
doing so, we first comment on the relation of the framework to design methodology and
practice and then make some remarks about its scope.
First of all, the above framework is not a phase model of the design process. Instead, as
remarked in Section 1, it is a rational reconstruction of steps that need to be taken in the use
and design of artefacts. In other words: these steps are not – as in a phase model – separated
by actual, explicit decisions, but they are reconstructed changes in intention. Consequently,
some phases of an actual design process may comprise several steps of our framework, e.g.,
decompositions of several components.
Being a rational reconstruction, our framework contains a number of idealisations. To name
two: cycles PD and AD are represented as plans of a single agent, whereas actual design is
usually a multi-agent process; and PD and AD are connected in such a way that artefacts are
embedded in a single user plan, whereas many artefacts are, in fact, hybrid or multi-purpose
ones. Concerning the first idealisation: our term ‘designer’ may be taken to designate any of
the parties involved in actual design, for instance, the board of a company in step PD.1, and
the marketing department in steps PD.2-4. But this partition and possible multiplication of PD
and AD may not always be this straightforward: introducing multiple agents may entail adding
co-ordination steps, reflecting the negotiations between agents. For instance: designers with
different backgrounds working in a design team may propose different decompositions, and
have to settle on one of them before integrating the design and adjusting the user plan. 13 The
case of hybrid artefacts, secondly, may be accommodated by including different client goals
in the PD cycle, which the designer seeks to contribute to by designing a single artefact. So,
for example, a designer may contribute to the client’s goals of sitting and sleeping
comfortably in a small room by designing a sofa bed. This solution is complicated by the fact
that the client may not wish to realise the various states of affairs simultaneously – as in the
case of the sofa bed – or that she may wish to realise incompatible states of affairs.
Finally, our action-theoretical framework, like most models of design, does not claim to
capture or explain the ‘creative leap’ 14 that takes place in conceptual design, or to pinpoint a
‘primary generator’. 15 It just describes a framework in which such design steps take place,
without making any assumptions about the nature of these steps.
As for the scope of the framework: we describe ‘design’ in general by taking product design
as our point of reference. The methodology of this design discipline is a mix – some would
say a hybrid – of the methodologies of architecture and mechanical engineering. We believe
that our framework may cover those disciplines as well, by focusing on some steps and
practically ignoring others. In the case of mechanical engineering, for instance, the AD cycle
will focus on technical development, and the role of the user in the PD cycle is limited. In
extreme cases, there is little need to take the user into account in steps PD.4 and PD.5,
because the user will be trained to use the machine that is being designed. If, on the other
Bucciarelli L L Designing Engineers MIT Press, Cambridge, MA (1994)
Cross N G and Dorst K Co-evolution of Problem and Solution Spaces in Creative Design in J Gero and M
L Maher (eds) Computational Models of Creative Design Key Centre of Design Computing and Cognition,
University of Sydney (1999) pp 243-262
15
Darke J The Primary Generator and the Design Process in N G Cross (ed) Developments in Design
Methodology Wiley, Chichester (1984).
13
14
10
hand, we apply the framework to architecture, the role of the architect in the overall process
of ‘building design’ determines the relevance of steps of our framework. For instance: if the
architect acts solely as the creative core of the overall process, and most of the technical
construction work is done by others, then the role of the architect might be sufficiently
described by the PD cycle only. In this case, we may have to expand the cycle to include a
more explicit construction of the user plan P, but this may be regarded as a change of focus
rather than one of principle.
The differences between design disciplines do not surface only in the way in which specific
steps in PD and AD are omitted. The nature of the steps in the AD cycle may be different for
the various disciplines. To give but one example: the importance of step AD.4 depends on the
way designers deal with the simulation of their designs in sketches, drawings, models and
prototypes. Design projects in mechanical engineering tend to go through an extensive
prototyping and testing stage, which is undesirable and perhaps even impossible in
architecture. In our opinion, the ease with which differences between the disciplines are
phrased in terms of our framework suggests the breadth of its scope.
Nevertheless, this scope is limited in another way: the framework only applies to ‘normal’
design activity, not to ‘inventions’. Although ‘invention’, as a rational process, will involve
most of the steps we described in the framework, it may ignore some crucial steps as well.
Some inventions have been purely technical developments done for their own sake; in
reconstructing them, most of the PD cycle can be skipped and the whole process focuses on
the AD cycle. In disregarding clients and considered use altogether, invention goes beyond
mechanical engineering and probably beyond the scope of our framework as well.
Bearing in mind these remarks, we apply the framework to a well-known and well-described
design method: QFD.
4
Quality Function Deployment
Quality Function Deployment (QFD) 16 has a number of features in common with our actiontheoretic framework: it forces the designer to consider explicitly the way in which users
employ artefacts and it helps with translating requirements of these users into design
decisions. Hence, QFD embeds design in the context of use. A comparison of this method
with our framework reveals, however, a number of shortcomings of QFD.
Following Bob King, we may take the following steps as a description of QFD:
Q.1 The designer identifies the requirements of users with respect to the artefact that is to be
designed or redesigned. These requirements are assigned relative weights.
Q.2 The designer identifies quantifiable characteristics 17 of the artefact that may fulfil the
user requirements, and the designer assigns target values that these characteristics have
to meet in order to actually satisfy the user requirements.
E.g., King B Better Design in Half the Time: Implementing QFD in America GOAL/QPC, Methuen, MA
(1989); Hauser J R and Clausing D The House of Quality Harvard Businesss Review May-June (1988) pp 6373; Akao Y (ed) Quality Function Deployment: Integrating Customer Requirements into Product Design
Productivity Press, Cambridge, MA (1990)
17
Examples of quantifiable characteristics are ‘the efficiency of the engine’ and ‘the energy needed to close a
door.’
16
11
Q.3 The designer determines the relationships between each user requirement and each
identified characteristic. If there is a strong correlation between satisfying a requirement
and meeting the target value of a characteristic, the relationship is captured by a value 9.
If the correlation is mediocre, weak or absent, it is captured by a 3, 1 or 0, respectively.
Q.4 The designer identifies the relationships between the characteristics themselves. These
relationships are represented by a p (for positive) if meeting the target value for one
helps meeting the target value for the other, and by an n if meeting one target value
conflicts with meeting the other.
Q.5 The designer adds up all requirement-characteristic relationship scores for each
characteristic (if desired after multiplying the scores by the relevant weight factors of
the user requirements).
Q.6 The designer determines priorities for realising the target values of the various
characteristics on the basis of the outcomes of this calculation. The highest scores are
for those characteristics whose target values relate most strongly to the important user
requirements; meeting these values can be given priority. The relationships between the
characteristics help the designer decide to work on characteristics that have many
negative relationships with other characteristics.
The method is visualised in a matrix, in which the rows are filled with user requirements plus
their relative weights, and the columns with artefact characteristics and their target values.
The matrix contains the relationships between the user requirements and the characteristics,
and the ‘roof’ on the matrix is used for the relationships between the characteristics
themselves. Because of this ‘roof’ the popular name for the matrix is ‘house of quality’ (see
figure 5).
User
Requirements
CharacteristicCharacteristic
Relationships
Artefact
Characteristics
Weight Factors
Prioritisation
RequirementCharacteristic
Relationships
Target Values
Figure 5. Visualisation of QFD in the ‘house of quality’.
12
Most of the literature on QFD describes the positive impact of the method on (marketoriented) product development. Only few articles emphasise more problematic aspects. 18
Here, we use our action-theoretical framework to identify four shortcomings of QFD. These
shortcomings arise because QFD presupposes a number of key steps in the design process.
First of all, comparing QFD to our AD cycle, we note that, to a large extent, QFD presupposes
the decisions AD.2 on how to describe the artefact. In step Q.2, for instance, one has to
identify quantifiable characteristics of the artefact. These characteristics may be properties of
the artefact as a whole (e.g., its weight), but they are usually properties of components of the
artefact (e.g., the efficiency of the engine). This latter identification, however, presupposes at
least one decomposition step AD.2.c.1, which the Q sequence offers no room for taking.
Hence, QFD seems to be a method for improving artefacts with a given decomposition
(redesign), rather than one that guides this decomposition.
Secondly, one can note that QFD does not deal with the functions of artefacts. Instead, QFD
presupposes that the decisions AD.2 have been made in such a way that the artefact already
possesses its functions. Hence, QFD does not address the design task central to the AD cycle,
of describing an object that has specific functions; it only is a method that enables the
designer to incorporate additional user wishes in the design.
Thirdly, comparing QFD with the PD cycle, we note that QFD does not include the decisions
PD.1-5. Hence, an artefact A is not explicitly embedded in a user plan that defines its
functions f, g, … and that relates the artefact to user goals. Instead QFD presupposes this user
plan and thus illustrates the primacy of artefacts over plans noted in section 2. The lack of an
explicit user plan and user group may cause difficulties for the steps Q.1 and Q.2. A study has
shown that this was probably the main reason for the failure of the Compact Disc Interactive
(CD-i) developed by Philips. 19
Related to this last point, QFD may, fourthly, run into problems when artefacts are used
within more that one user plan. Consider, for instance, all-terrain cars. These are traditionally
used by people who need to travel across rough and muddy terrain. But nowadays they are
also used by people who drive only on properly paved roads in built-up areas in order to show
off. These two groups of people have different plans in which they use all-terrain cars, and
probably formulate different requirements on the basis of their respective plans. A city user
may wish to have additional rear-view mirrors for parking safely, whereas the traditional user
may wish that items attached to the car are kept to a minimum in order to make it more
robust. QFD is unable to discriminate between these different requirements and may thus lead
to design priorities that do not cohere with a user’s ends.
A valuable ingredient of QFD is the explicit comparison of the relations between the different
characteristics of an artefact in step Q.4 and Q.6 in the ‘roof’ of the matrix. This comparison
helps the designer to integrate these characteristics by revealing possible design conflicts. By
replacing the characteristics by components, these steps may be helpful for the integration
described in step AD.2.c.3.
Sarlemijn A and Boddendijk H G (eds) Produkten op Maat: QFD als Gids bij Productcreaties Boom,
Amsterdam (1995) chapters 8-11; De Vries M J Teaching Philosophy and Methodology of Technology to the
Future European Engineer Manager, Forthcoming in New Horizons in Industry and Education Proceedings of
the International Conference on New Horizons in Industry and Education, Santorini (1999) chapter 6.5
19
Sarlemijn A Methodologie van Technolgiemanagement: QFD als Instrument in Sarlemijn A and
Boddendijk H G (eds) Produkten op Maat: QFD als Gids bij Productcreaties Boom, Amsterdam (1995) p 67
18
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5
Connecting the framework to the philosophy of artefacts
Our action-theoretical framework has philosophical repercussions as well. In this section, we
shall present some consequences for the philosophy of artefacts and their functions.
First of all, on our account, artefacts cannot be understood as objects either used or designed
for a certain purpose. Instead, we describe artefacts as objects playing a role in the contexts of
both use and design, contexts that are mediated by the communication of a user plan. This
description is similar to that given by Randall Dipert in his monograph on artefacts, although
Dipert appeals to communicated intentions in general rather than to a communicated user
plan. 20
At the end of Section 1, we argued that the rationality of a use cycle may be based on beliefs
about the physical properties of these objects, existing practices, or the design of a user plan
and objects. We chose to designate as artefacts only a class of objects involved in the third
kind of justification, i.e., objects that have been the result of PD and AD cycles. So not all
used objects are artefacts: a stone used for breaking a window is not an artefact if it is chosen
because of its hardness or because it has been handed down the generations as an appropriate
means. Perhaps less intuitively, objects that are the product of an AD cycle, but not a PD
cycle, are not artefacts: something that has been made, but is not embedded in a user plan by
the designer, does not have a function and cannot be called an artefact. This is a conceptual
point rather than one supported by a wealth of examples, but perhaps designed components of
an artefact that play no role in use, or contraptions built from all the Lego blocks a child
possesses for the exclusive purpose of using all blocks might be regarded as designed, but
non-artefactual objects.
Furthermore, note that our account of artefacts is action-theoretical rather than metaphysical.
We describe artefacts in terms of their intentional history and role. This role may be different
for different agents, and one object may even play different roles at the same time. The wiring
of an electric light is designed to provide it with electricity, and is used as such: the users
connect it to a power source and make sure it is sufficiently isolated. So the wire may be
called an artefact in our sense. But at the same time, many users use the wire to hang the light
from. This is standard practice rather than something intended by the designer or included in
the communicated user plan. So, in this sense, the wire is not an artefact. On a metaphysical
account, this is absurd: nothing is both A and not-A at the same time.
Another consequence of our account is that artefacts cannot be exclusively described, even
action-theoretically, in terms of their function. Artefacts are products of cycle AD as well as
PD. This distinguishes them from non-designed objects, such as water and air, that are
included in user plans. As outlined in Section 2, cycle AD terminates by referring to either
design by others (AD.2.b) or to physical structure (AD.2.a). Since design by others again calls
for a combination of PD and AD cycles, all designers can be said to appeal to physical
structure in the end. Therefore, artefacts are to be described in terms of both function and
20
Dipert R R Artifacts, Art Works, and Agency Temple University Press, Philadelphia (1993)
14
structure. The metaphysical counterpart of this result, which is suggested but certainly not
entailed by it, may be called the thesis of the dual nature of technical artefacts. 21
Finally, when applied to the philosophy of functions, our account seems to fit in with Robert
Cummins’ analysis. 22 In this analysis the assignment of a function to an item is taken as an
assignment of a disposition to that item with which a disposition of a larger system (of which
the item is a part) can be (partly) explained. Thus, the wing of an aeroplane is assigned the
function ‘providing lift’ because it has ‘providing lift’ as a disposition and because this
disposition partly explains the plane’s disposition to fly. The functions f, g, … that our
account assigns to artefacts in step PD.4 can thus be understood as Cummins functions: the
user plan P devised in that same step has the disposition ‘realising state of affairs φ’; and the
functions of artefact A corresponding to the dispositions ‘f-ing’, ‘g-ing’, … explain (partly)
that P has this disposition. Moreover, the functions that our account assigns to components
O1, O2, … in step AD.2.c.1 are Cummins functions, but now with respect to the composite
system O1+O2+ ⋅⋅⋅: these functions of O1, O2, … explain the dispositions ‘f-ing’, ‘g-ing’, … of
the composite O1+O2+ ⋅⋅⋅ that correspond to the functions of that composite. This is not to say,
however, that our account of functions is exhausted by Cummins’. His theory is notoriously
unable to account for the normativity imposed on the function. On our account, function is
closely connected to use and design, which are subject to standards of rationality, which could
thus transfer to function itself. Hence, unlike Cummins, we may be able to account for
normativity.
6
Conclusions
In this paper we have analysed designing in terms of cycles of intentional action. We started
our analysis by considering the context of use. Users bring about their goals by carrying out
user plans, which may include the use of objects. Then we noted that in some cases these user
plans are designed by a designer, and we gave an action-theoretical description PD of this
process of user plan design. Finally we noted that a designer may, in addition to the user plan,
also design the objects that are to be used in that user plan. We have identified these objects as
artefacts, and defined the functions of these artefacts in terms of the states of affairs they are
supposed to bring about. And we gave an action-theoretical description AD of the process of
artefact design.
In our analysis the notion of a ‘user plan’ plays a central role. The process of designing is
primarily focussed on the design of those users plans and only subordinately aimed at the
design of artefacts. And user plans are the means with which designers contribute to the
attainment of the goals of users by those users. Moreover, we have argued that our analysis is
fairly general in the sense that it can be applied to different design disciplines ranging from
mechanical engineering to architecture. And it can be used to criticise existing design
methodologies, as we did with QFD. Finally we have indicated the consequences of our
analysis for the understanding of the concept of an artefact and its function.
We have confessed, on the other hand, that our analysis ignores a number of aspects of
design. It does not reflect the creativity involved in the various design decisions. And it does
This paper has partly been written in the context of a philosophical research program that takes this dual nature
of technical artefacts as its point of departure (see http://www.dualnature.tudelft.nl/ as well as Kroes P Design
Methodology and the Nature of Technical Artefacts in this issue of Design Studies).
22
Cummins R Functional Analysis Journal of Philosophy Vol 72 (1975) pp 741-765
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not yet describe the interactions between the various agents in the case that not one designer,
but a number of agents are involved in the design processes PD and AD. With respect to this
latter point, our analysis can indeed be developed. Other candidate issues that can be taken up
are the following two. Firstly, more needs to be said about the way designers subdivide their
design problem and try to reach a certain level of integration and coherence in artefact design.
Therefore, a next step in this research project will be to reformulate the strategies found in
design methodology 23 in terms of this conceptual framework. Secondly, our analysis offers
possibilities for clarifying the normativity involved in design and use. In this paper,
normativity was tied to the rationality of planned action in general and the means-end
coherence of plans in particular. This may lead to several norms for ‘good’ and ‘bad’ design
and use. Yet these probably do not exhaust the normativity involved in both contexts. For, as
said in Section 1, our approach shows an intellectualist bias, leading to an interpretation of
normativity in terms of rational deliberation only. An analysis of design and use as actual
operations in an environment may be the biggest issue left unresolved here.
Acknowledgements
The authors would like to thank Michiel Brumsen, Maarten Franssen, Peter Kroes, Anthonie
Meijers, Ibo van de Poel, Marcel Scheele and an anonymous referee of this journal for their
comments on earlier drafts of this paper, and Randall Dipert for both his comments and the
presentation of a model of artefacts that stimulated research on this paper. The research by
Wybo Houkes and Pieter Vermaas was supported by the Netherlands Organisation of
Scientific Research (NWO).
E.g., Dorst C H Describing Design: A Comparison of Paradigms PhD thesis, Delft University of Technology
(1997); Dylla N Denk- und Handlungsablaüfe beim Konstruieren Hanser, München (1991)
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