Study on Latent Function for Sustainable Design
Feature extraction in Latent Function discovery process
Kazusa Minami*, Yukari Nagai **and Toshiharu Taura ***
* School of Knowledge Science, Japan Advanced Institute of Science and Technology, Japan
kaz-mina@ jaist.ac.jp.
** School of Knowledge Science, Japan Advanced Institute of Science and Technology, Japan
ynagai@ jaist.ac.jp.
*** Graduate School of Science and Technology, Kobe University, Japan
taura@ mech.kobe-u.ac.jp.
Abstract: Environmental problems have become an important issue in our society. In the design
field, a new type of artifact has been pursued. In this study, the authors focus attention on the idea
of “Latent Function”. When an entity is exposed to a circumstance, a peculiar behavior is
manifested corresponding to the circumstance. This behaviour is called the Visible Function.
Different behaviours are observed under different circumstances. The total of these behaviours is
called the Latent Function. As the circumstance, we can consider the state of the user’s mind, as
well as physical conditions, such as temperature. Namely, the way of using an artifact will change
when the user changes. On the other hand, for the same user, some artifacts are easily applied to
various usages (functions), while other artifacts are not. If the number of artifacts with abundant
Latent Function increases in society, the decrease of wasteful action and the improvement of
recycling will be expected. In this study, the features of the users’ discovery process of Latent
Function of an artifact are extracted. As the mechanism of the discovery of a new usage by users,
the authors focus on not only the direct discovery process from the artifact, but also that from the
decomposed components (for instance, at the material level). In this process, the same Latent
Function as that found by the discovery process from the components should be discovered.
Concerning the mechanism of discovering a new usage, the relationship between the Latent
Function of the artifact and that of its component is analyzed by a questionnaire survey. We found
that more Latent Functions were discovered from a component than from the artifact. The
proportion of Latent Functions discovered from artifacts to Latent Functions discovered from
components was very low. Therefore, for artifacts suitable for an environmentally conscious
society, easy decomposition in the user’s mind, whereby creative Latent Functions can be easily
discovered from the decomposed components, is desirable. In this paper, the experiments on Latent
Function discovery by users is reported and discussed.
Key words: Sustainable design, Latent Function, Environment, Artifact
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1. Introduction
In the pursuit of an affluent lifestyle, man has made numerous artifacts. However, design based on mass
production and mass consumption causes the drying up of resources and environmental pollution. We should
work on the formation of a sustainable society if we wish to continue using the limited natural resources. We
should review all the production stages such as design, production, circulation, consumption, use, recycle, reuse,
and abandonment from the standpoint of reducing the load on the global environment. The basic idea of making
high technology and environmental issues compatible through the idea of "Eco-design" with respect to the
environmentally friendly product has extended accelerating. Various kinds of research are carried out on
environmental design and environmental evaluation of an artifact, and the result has improved gradually [1].
However, much of the research involves top-down methods from the producer. Sustainable artifacts for the user
have not been discussed. The top-down idea is contradictory to a sustainable society, and it becomes necessary to
search for a new type of artifact [2]. In this study, the authors focus attention on the idea of "Latent Function” as
described in the next chapter, and we undertake to construct a Sustainable Design methodology for the user.
Therefore, it is necessary to analyze the features of the artifact from the viewpoint of Latent Function. In this
paper, we focus attention on the process by which the user thinks about the Latent Function, and the features of
artifacts with abundant Latent Function are extracted.
2. Latent Function
When an entity is exposed to a circumstance, a peculiar behavior is manifested corresponding to the
circumstance. This behaviour is called the Visible Function. Different behaviours are observed for different
circumstances. The total of these behaviours is called the Latent Function [3]. The circumstance is considered to
be the state of the user’s mind, as well as physical conditions, such as temperature [4]. Namely, the way of using
an artifact will change when the user changes. On the other hand, for the same user, some artifacts are easily
applied to various usages (functions), while other artifacts are not. If the number of artifacts with abundant
Latent Function increases in society, the user can continuously discover new functions. This is expected to lead
to the decrease of wasteful action and the improvement of recycling. In this study, we undertake to construct a
method of designing artifacts with a high degree of Latent Function. However, Latent Function is doubted as
being inferior to a Visible Function that has been manifested by another artifact specifically designed for that
function. For instance, even if a beer bottle can be used as a flower vase, it is nothing but a substitution for real
flower vase. The authors feel that a truly rich sustainable society cannot be achieved by such substitutional
function. The authors pursue the implementation of not a substitutional function, but a more creative Latent
Function in an artifact. First, to examine the features of artifacts with abundant Latent Function, the features of
the users’ discovery process of Latent Function of an artifact are extracted.
3. Process of discovery of new usage
In this study, as the mechanism of discovery of a new usage by users, the authors focus on not only the
direct discovery process from the artifact, but also that from the decomposed components (for instance, at the
material level). The relationship between the Latent Function of the artifact and that of the component is
mathematically described as follows. When artifact A consists of α, β and γ, artifact A is described as
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α ⊕ β ⊕ γ =A
( ⊕ means assemble).
(1)
The number of Latent Functions of components is assumed to be α’, β’ and γ’. The number of Latent Functions
of artifact A is expected to be
α’ + β’ + γ’ = A’ ( 0≦α’, 0≦β’, 0≦γ’ ).
(2)
Therefore, the number of Latent Functions of the artifact and those of the components should be α’≦A’, β’≦A’
and γ’≦A’ . Theoretically, if the artifact is decomposed and Latent Functions of the decomposed components are
discovered, many more Latent Functions should be discovered than those from only one component. In this
process of decomposing the artifact and discovering Latent Functions from the decomposed components, the
Latent Function of the artifact should be included in that found by the process of discovery from the components.
4. Evaluation
Concerning the mechanism of discovering a new usage, the relationship between the Latent Function of
the artifact and that of the component is analyzed by a questionnaire survey. The investigated artifacts are a desk,
a television, a chest of drawers, a pane (sheet glass), wood, and a kitchen knife. Among these six articles, the
television and pane, desk and wood, chest of drawers and wood are pairs. Each pair is a combination of artifacts
that should be decomposed into some components and artifact’s component. Component of the television is
thought to be the pane, and a component of the desk is thought to be the wood. Therefore, the above-mentioned
pairs were selected.
5. Analytical procedure
The Latent Function of an artifact is determining by the following procedures.
5.1 Enumeration of Latent Function
In the experiment, three subjects are asked to find as many Latent Functions as possible from a desk, a
television, a chest of drawers, a pane, wood, and a kitchen knife in ten minutes. The responses are given as the
name of the artifact providing the new function, instead of the function name. For instance, responses to “Think
about new uses of a bucket”, are a washtub, helmet, water tank, and chair. In this investigation, in order to obtain
many Latent Functions, processes (disassembly, cutting and welding, etc.) that are, in reality, impossible for the
artifact are allowed.
5.2 Judgment of Latent Function
The obtained data is analyzed by judging whether the newly discovered function is an actual Latent
Function or not, using the EDR Concept Dictionary [5]. The discovered function whose higher level concept is
the same as the original visible function is judged not to be a Latent Function. Table 1 shows the example of the
desk. A higher level concept of the desk is an "artifact made to put thing on it", therefore, functions such as a
stool, table, and chair, which belong to the class of an "artifact made to put things on it" are judged not to be
Latent Functions of the desk. Therefore, the first ten answers are decreased to 7.
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Table 1 Judgment of Latent Functions of desk
1
2
3
4
5
6
7
8
9
10
answer
shelter
place of refuge
stool
case
table
white board
shelf
drawer
weight
chair
Latent Function
shelter
place of refuge
case
white board
shelf
drawer
weight
total
10
7
5.3 Unification of Overlapping Latent Function
Responses obtained for Latent Function may overlap many times. Therefore, newly discovered Latent
Functions that are similar to other ones are grouped together. The higher level concept of the answer obtained
because of analysis 5.2 is examined. At this time, answers which correspond to the concept being examined are
combined. Table 2 shows the example of the desk. Because shelter and place of refuge have the common higher
level concept “apparatus to prevent accident”, they are grouped together. Similarly, because case are and drawer
have the common higher level concept “box”, they are grouped together. Consequently, the Latent Functions of
the desk are limited to 5 in number.
Table 2 Unification of Latent Functions of desk
1
2
3
4
5
6
7
8
9
10
total
Latent Function
shelter
place of refuge
unification of Latent Function
apparatus to prevent accident
case
box
white board
shelf
drawer
weight
white board
shelf
weight
7
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5.4 Proportion of Latent Functions of the artifact to Latent Functions of its components
For desk & wood, television & pane and chest of drawers & wood, the proportion of Latent Functions
discovered from the artifact to Latent Functions discovered from the components is calculated. Using the results,
the discovered Latent Functions were compared among the three pairs.
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6. Example
Table 3 shows the adjusted results of the analytical procedure. The limited proportion of the number of
answers for the desk, television, chest of drawers, pane, wood, and kitchen knife are 46%, 10%, 42%, 19%, 14%
and 34%. The number of answers was markedly decreased for the desk and the chest of drawers.
Table 3 Adjustment result of the analysis technique
1
2
3
4
5
6
artifact
Number of answers Number of Latent FunctionｓLimited proportion [%]
desk
13
7
46
television
10
9
10
chest of drawers
10
6
42
pane
17
14
19
wood
18
15
14
kitchen knife
8
6
34
Fig. 1 shows the numbers of Latent Functions of artifacts obtained in this investigation.
The average numbers of Latent Functions discovered from the desk, television and chest of drawers are seven,
nine and eight, respectively. On the other hand, the average numbers of Latent Functions discovered from the
components wood and pane are fifteen and fourteen. Therefore, many more Latent Functions were discovered
from the components than from the artifacts. Table 4 shows the proportions of Latent Functions of the artifact to
the Latent Functions of the component. They are 14%, 20% and 13% for desk & wood, television & pane and
chest of drawers & wood, respectively. Therefore, the proportion of Latent Functions discovered from an
artifact to the Latent Functions discovered from a component was very low.
25
Number of Latent Functions
20
subjectA
15
subjectB
subjectC
10
5
0
desk
television chest of
drawers
pane
wood
kitchen
knife
Fig.1 Number of discoveries of Latent Functions
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Table 4 Discovery rate of Latent Function
desk & wood
subject A
16
subject B
7
subject C
18
average
14
Discovery rate of Latent Function[%]
television & pane chest of drawers & wood
40
16
5
13
17
9
20
13
average
24
8
15
16
7. Conclusion
In this study, to examine the features of artifacts with abundant Latent Functions, the features of the users’
discovery process of Latent Functions of an artifact were extracted. In the above investigation, more Latent
Functions were discovered from a component (glass and wood, etc.) than from an artifact (television and desk,
etc.). The proportion of Latent Functions discovered from artifacts to Latent Functions discovered from
components was very low. Therefore, for artifacts suitable for an environmentally conscious society, easy
decomposition in the user’s mind, whereby creative Latent Functions can be easily discovered from the
decomposed components, is desirable. Also, discovering many Latent Functions might lead to the discovery of a
more creative Latent Function. In this study, the relationship between Latent Functions discovered from an
artifact and from a component was able to be shown. However, this result differed from that hypothesized. To
clarify the reason for this, it is necessary to discuss the entire investigation method. When a subject seeks a
Latent Function from an artifact that consists of many components, the subject looks for a Latent Function that
uses all components. Therefore, it is thought that the subject did not consider Latent Functions of only one
component. For instance, even if the subject discovers a Latent Function using only the glass component of the
television, many other components remain unused. Therefore, there is the possibility that the subject judged a
Latent Function that uses only glass to be inapposite. We will advance the discussion on the mechanism of
discovery of a new usage by users, and construct a Sustainable Design Method.
References
[1] Behrendt, S., 1997, Life Cycle Design : A Manual for Small and Medium-Sized Enterprises, Springer
[2] Yamamoto, R., 1999, Senryaku Kankyo Keiei EcoDesign, DIAMOND Inc. (in Japanese).
[3] Yoshikawa, H., 1981, General Design Theory and a CAD System, Man-Machine Communication in
CAD/CAM, pp. 35-58.
[4] Ohkoshi, K. and Taura, T., 2003, Ecological Adaptability by Estimating Latent Function of Artifacts,
Manufacturing Systems Division Conference 2003, pp. 49-50.
[5] National Institute of Information and Communications Technology, 2005, Concept Dictionary, CPD-V030,
EDR Electronic Dictionary.
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