determining latent functions by focusing on the … if a latent function of “planting flowers”...

Determining Latent Functions by Focusing on the Purposes of

Products

Yuki Murota*, Toshiharu Taura**, Akira Tsumaya***

*Kobe University, [email protected]

** Kobe University, [email protected]

*** Kobe University, [email protected]

Abstract: A product, when used in a certain field, manifests the function that is intended by the designer. However, products used in different fields (latent fields) may manifest different functions (latent functions) that may lead to valuable discoveries. From the perspective of product safety and in order to create innovative functions, it has become increasingly important to consider the fields in which products are used and their potential hidden functions. This paper discusses and proposes a method for discovering the latent functions and latent fields of products by focusing on their purposes. If two products share the same purpose, one of the products may be substituted for the other and manifest its visible function as a latent function. First, aspects of the purposes of products are discussed and systematized with reference to related studies. Next, a procedure and a computer system to determine latent functions and their latent fields are created. The authors then conduct a case study using this system, which shows the effectiveness of the proposed method. Key words: Function, Latent Function, Field, Latent Field, Purpose

1. Introduction

Products are designed with consideration of the function and place in which they will be used. For example, a chair is designed for the function of “sitting on” and used with a table in a living room. However, products may also manifest implicit functions in addition to those that are intended by designers. In the previous example, the chair may be used as a hanger with the function of “hanging clothes,” or as a step with the function of “lifting a human higher,” if he or she needs to reach for something on a high shelf. In General Design Theory, these types of functions, which the designers did not originally intend but which may be manifested in another situation, are called “latent functions.” In this theory, latent functions are defined as “different functions that manifest under different circumstances,” whereas a function satisfying the requirements provided by a designer is defined as a visible function. The circumstances that cause a visible function are defined as the field [3].

Latent functions may cause dangerous situations for users. For example, an electric bulb that is normally used to illuminate a room has a function of “lighting up things.” However, if a user inadvertently touches it, a latent function of “heating things” is actualized and leads to burned hands. Designers are expected to design products so that such harmful latent functions do not appear.

On the other hand, latent functions may add new value to products for users. For example, an empty bottle may be used as a pen stand if a latent function of “gathering pens” is discovered and may also be used as a flowerpot if a latent function of “planting flowers” is discovered. These are examples in which new usages are created by actualizing latent functions. Considering such latent functions may increase the reuse of products.

As described above, latent functions are useful in the realization of “safety manufacturing” and “sustainable manufacturing.” Hence, when designing products, it is important to examine their latent functions as well as their

2263

Consilence and Innovation in Design - Proceedings and Program5th IASDR 2013 TOKYO5th International Congress of International Association of Societies of Design Research

2250


2260


2259


2258


visible functions. The authors previously focused on the latent functions that are inherent in products and proposed a method for discovering them (hereafter referred to as latent function inferring) [1]. The authors thought that the latent functions of one product are analogized from the visible functions of another product, if both products have a similar lower-level function structure. In this paper, the authors propose another method to infer latent functions and their fields from a different viewpoint. Specifically, the authors focus on the “purposes” of products to infer the products’ latent functions and their fields.

This paper is organized into 5 chapters. In Chapter 2, the authors’ previous study of “latent function inferring” is introduced. In Chapter 3, the authors discuss the “purposes” of products as a new viewpoint for latent function inferring. The fields in which products are used is also discussed. Based on these discussions, a new method of inferring latent functions on the basis of a product’s “purpose” is proposed. In Chapter 4, based on the method proposed above, a computer system for inferring latent functions is developed and the effectiveness of the proposed method is verified. Chapter 5 contains the conclusion and areas for further discussion.

2. Inferring Latent Function by Focusing on Lower-level Functions

When using the above definition of “latent function,” it is necessary to identify all of a product’s behaviors in order to derive the latent function. However, this is difficult, particularly when designing complicated products. In addition, functions are subjectively perceived concepts and vary with the individual user.

Moreover, not all behaviors can be considered latent functions. Therefore, another approach should be developed that does not rely on directly identifying all of a product’s behaviors in advance.

In their previous study, the authors created the following method to derive latent functions. Let us consider a “car” as an example. A car has the latent function of “pressing against the ground.” Here, this latent function can be represented as the function of “road roller.” In other words, the latent functions of a product are analogized from the functions of other products. On the basis of this consideration, the authors analyzed the kind of relationship that exists between the target and base products in the analogy framework, wherein the function of the base product can be transferred to the target product [1]. As a result, it was revealed that the target product (in the above example, a car) and the base product (in the above example, a road roller) had similar lower-level functions. In the above example, there was a similarity between “engine turns tire,” which is a lower-level function of a car, and “engine turns roller,” which is a lower-level function of a road roller. This example suggests that the visible function of the base product (a road roller) can be the latent function of the target product (a car) under the condition that both products are able to be manifest the same function (“pressing against the ground”) and that both products contain a similar mechanism to realize it. Conversely, it is assumed that the latent function can be analogized by referring to a product with a similar mechanism.

In the previous study[2], a function was defined as “an entity’s behavior that plays a special role” and described by using a subject (S), verb (V), and object (O). In addition, for a visible function of a product, f1 =

(S1,V1,O1), a latent function of the same product was defined as a role that appears when the product (S1) exerts a different action (V2 ) on a different object (O2 ). Accordingly, the operation of function transfer was proposed as the method to find a latent function by “analogy.” As shown in Figure 1, this operation replaced verb V1 and object O1 of the function f1 = (S1,V1,O1) (hereafter referred to as the target function) with verb V2 and object O2 of some other function f2 = (S2,V2,O2) (hereafter referred to as the base function). This method focused on the similarity between the products’ lower-level functions, breaking the function down into its individual details rather than by examining the functions that were observed for the product as a whole.

Figure1. Function transfer

),,( 2222 OVSf ),,( 1111 OVSf

),,( 2211 OVSfnew

2264


2251


2261


2260


2259


3. Inferring Latent Function by Focusing on the Purpose of Products

3.1. New approach to latent function inferring

Usually, products are designed to achieve a particular purpose. For example, a “car” is designed for the purpose of “moving objects or humans,” and a car manifests a function of “carrying objects or humans” to achieve this purpose.

The authors thought that latent functions could be analogized by focusing on the purposes for which products are used as well as by focusing on the similarity of lower-level functions. Let us consider the example of a mowing machine and burner. To cut grass that grows in a yard, we use a mowing machine that manifests the function of “cutting the grass.” However, a burner —which has the original function “burn objects”—can be substituted for this purpose. This substitution is possible because the purpose of both functions is to “remove an object,” and therefore the same result is expected. Accordingly, a burner is considered to have the latent function “burn grass” in the yard. This example implies that a product may be substituted for another product and manifest the latent function as a visible function in another product’s field if it shares the same purpose.

3.2. Purpose of products

3.2.1. Consideration of the purposes of products

To clarify “the purpose of a product” and “how the purpose is described,” the authors refer to the discussion of the relationship between “purpose” and “means” in teleology.

In teleology, “purpose” is defined as that which is achieved by “means.” This implies that a causal connection exists between “purpose” and “means.” In this study, the authors extend this discussion by considering that the purpose of a product is “the result after the functions manifest” and the functions of a product are “the means to achieve the purpose.”

Next, let us consider how the “purpose” of a product is described. The “purposes” of products are usually described as “the actions for which people use products.” This can be explained by using the examples of “oven” and “mixer.” The functions of oven and mixer are described as “oven bake food” and “mixer mix food” respectively by using a set of subject (S), verb (V), and object (O). Here, the “purpose” of both “oven” and “mixer” is “to cook food,” which is the result after the functions have manifested.” Then, the “purpose” is said to be that which is generated after the functions are manifested. This consideration implies that “purposes” are not actions that are abstracted from the functions. For example, the functions of “kitchen knife” and “chainsaw” are described as “kitchen knife cuts food” and “chainsaw cuts wood.” According to the previous definition, the purposes of these products are to “cut objects,” which is an abstraction of each function. However, we should notice that the kitchen knife is used in order “to cook food” and the chainsaw is used in order “to create objects,” actions that can be achieved after each function has manifested. Accordingly, the authors believe that they should pay attention to the action that becomes possible after the functions are manifested.

3.2.2. Definition of the purposes of products

On the basis of the above consideration, the authors define the “purposes” and “functions” of products as follows.

Purpose of product:

The purpose of a product is the action that people want to complete by using the product and is described by a set of a verb (V) and an object (O)

Function:

The function is the means to achieve the purpose and is described by a set of a subject (S), verb (V)，and an object (O).

The relationship between function and purpose is as follows:

2265


2252


2262


2261


2260


・The purpose of a product is the result after the functions have manifested. ・Function, fu=(S fu,V fu,O fu), and purpose, pu=(Vpu,Opu), have the following relationships: pufu VV

pufu OO pufu OOor

For example, the purpose and function of a clothes washer are described as “clean object” and “a clothes

washer washes clothes.”

3.3. Fields

3.3.1. Consideration of fields

Latent functions are those that are manifested under different circumstances, as introduced in section 1. This statement implies that we should focus on “circumstances” in order to find the latent functions. This study uses the term “fields” in order to capture the notion of the “circumstances” of products. Here, the authors would like to discuss how “fields” are defined and what kinds of “fields” exist. Let us consider an example of an “electric bulb.” The visible function of an electric bulb is “electric bulb lights up things,” and this function is manifested under the condition that “there exist people who manipulate the electric bulb,” “there exists the place where an electric bulb is used,” and “there exists an object to light up.” These existences are strongly related to “fields.”

3.3.2. Definition of fields

On the basis of the above consideration, we define the fields as follows:

Fields:

Fields are the circumstances that cause the functions to manifest. The fields are classified into “person who

uses products,” “object of function,” and “place where the products are used.”

Visible function and latent functions are defined as follows:

Visible fields:

The field (A) in which the visible function (a) is manifested.

Latent fields:

The field (B) in which the other different (latent) function (b) is manifested by the same product.

The relationship between visible function, latent function, visible field, and latent field is illustrated in

Figure 2.

Figure.2 Relationship between visible/latent function and visible/latent field

2266


2253


2263


2262


2261


Figure.3 Function transfer

3.4. Process of inferring latent function by focusing on the purpose of a product

3.4.1. Consideration of function transfer by focusing on the purpose of a product

Let us consider how the function is transferred when the purposes of products are focused on. In the authors’

previous study, function transfer is defined as “replacing verb V1 and object O1 of the target function f1 =

(S1,V1,O1) with verb V2 and object O2 of some other base function f2 = (S2,V2,O2).” However, when we focus on

the purposes of products, the previous method cannot be applied. This can be explained with the example of

“mower” and “burner.” Here, the target product is “mower” and the base product is “burner”; the functions are

“mower cuts grass” and “burner burns object” respectively; and the purpose of both products is “remove object.”

If the purpose “burn object” is transferred from the “burner” to the “mower” according to the previous method, the

latent function “mower burns object” is obtained, but this function is inappropriate in common-sense terms. This

is because the similarity between the lower-level functions of the target and base product, the condition in the

previous method, is not valid. Accordingly, in this study, a latent function is inferred by replacing only the object.

Furthermore, the fields (latent field) are also inferred.

Function transfer:

By focusing on the purposes of products, the authors conclude that function transfer involves replacing the

object O1 fu of a target product’s visible function, fu1 = (S1

fu,V1 fu,O1

fu), which is manifested, and visible fields, fi1=

(X1,Y1), with object O2 fu of the base product’s visible function, fu2 = (S2

fu,V2 fu,O2

fu), and the fields (latent field),

fi2= (X2,Y2). Here, X is a person who uses the products; Y is a place where products are used. This process is

illustrated in Figure 3.

3.4.2. Formulation of the latent function inference process

The latent function inference process, which uses the similarity in the purposes of products for function transfer, is formulated as follows:

),(),,(

),,()(

),(),,(),(),,(

),,(),,,(),,(),,,(},,{

:

221

2111

11111

21

222111

222111

22221111

2222111121

11

YXfi

OVSfu

pufifuPlp

pupuwhen

OVpuOVpu

YXfiYXfi

OVSfuOVSfu

pufifuppufifupppP

pPl

new

fufufunew

newnewnew

pupupupu

fufufufufufu

newl

(1)

Here, P denotes the target product (p1) and base product (p2), pu1 denotes the purpose of p1, pu2 denotes the purpose of p2, fu1

new denotes the latent function of the target product (p1), and fi1new denotes the latent fields

),,( 2222fufufu

OVSfu ),,( 1111fufufu

OVSfu

),( 111 YXfi ),( 222 YXfi

),,( 2111fufufunew

OVSfu

),( 221 YXfinew

2267


2254


2264


2263


2262


corresponding to fu1new. An example is presented in Figure 4. Here, “remove object,” which is the purpose of the

burner, and “remove object,” which is the purpose of the mower, are found to be same. Accordingly, “grass,” in the visible function of “mower,” and its visible field, “adult, yard,” are transferred to “burner.” As a result, the latent function “burner burns grass” and the latent field “adult, yard” are obtained.

4. Development of Computer System for Latent Function Inferring

Based on the method proposed above, the authors developed a computer system for inferring latent functions. In addition, a product database containing the visible function, visible fields, and purpose of 28 products was prepared. In this system, following the input of the target product by the user, a product’s latent functions can be inferred.

In order to confirm the feasibility of the proposed method and developed computer system, the authors conducted an experiment. In this experiment, the latent function “burner burn grass” and its latent field “adult, yard,” which was illustrated as an example in the previous section, could be inferred.

Furthermore, another case study was conducted, as shown in Figure 5. In this case study, “electrical toothbrush” was first selected as a target product and “dish washer” was selected as a base product. Next, the purposes of both products were found to be same. Accordingly, that latent function “electric toothbrush brushes dish” and its latent

fields “person, kitchen” were inferred by function transfer from the visible function “dish washer washes dish”

and its visible field “person, kitchen.” The latent function “electrical toothbrush brushes dish” could not be

inferred through the previous method, because the lower-level functions of the two products were not the same. In

another case study, the latent function “air-gun fires water” of an air-gun and its latent field “child, outdoors” were

inferred (Figure 6). Although the latent function “air-gun fires water” is difficult to understand, its latent fields

(“child, outdoors”) suggest its usage. The latent function “electrical toothbrush brushes dish” and its latent fields “person, kitchen” suggest new

values or new uses for an electrical toothbrush. Meanwhile, the latent function “air-gun fires water” and its latent

fields “child, outdoors” show an incorrect use of an air-gun by a child. This information can help a designer

design more innovative and safer products if it is presented in advance. These results show the effectiveness of the

proposed method.

Figure.4 Example of latent function inferring

S1fu burner

V1fu burns

O1fu object

X1 adult

Y1 outdoor

V1pu remove

O1pu object

p1 : burner

S2fu mower

V2fu cuts

O2fu grass

X2 adult

Y2 yard

V2pu remove

O2pu object

p2 : mowermatch

transfer

Infer fu1new,fi1

new

The latent function and fields of burner are inferred asfu1

new = (burner, burns, grass)fi1

new= (adult ,yard)

2268


2255


2265


2264


2263


Figure.5 Inferring latent functions of “electrical toothbrush”

Figure.6 Inferring the latent functions of “air-gun”

5. Conclusion

In this study, the authors proposed and formulated a method for inferring a product’s latent function by focusing on the notions of “purpose of products” and “fields.” Based on the proposed method, the authors developed a computer system for inferring latent functions. From the results of case studies, the authors confirmed the effectiveness of the proposed method.

However, some inappropriate latent functions may still be created. The authors therefore intend to investigate methods for reducing these inappropriate functions. In addition, the appropriateness of the created latent functions was evaluated by the authors subjectively. It is necessary to consider criteria for determining this objectively.

Acknowledgements

This work was supported by KAKEN (24603012).

S1fu

electrical

toothbrush

V1fu brushes

O1fu tooth

X1 all people

Y1 lavatory

V1pu clean

O1pu object

p1 : electrical

toothbrush

S2fu dish washer

V2fu washes

O2fu dish

X2 woman

Y2 kitchen

V2pu clean

O2pu object

p2 : dish washermatch

transfer

Infer fuppernew

The latent function and fields of electrical toothbrush are inferred asfu1

new= (electrical toothbrush, brushes, dish)fi1

new= (woman, kitchen)

Infer fu1new,fi1

new

S1fu air-gun

V1fu fires

O1fu ball bullet

X1 adult

Y1 outdoor

V1pu enjoy

O1pu oneself

p1 : air-gun

S2fu water-gun

V2fu fires

O2fu water

X2 child

Y2 outdoor

V2pu enjoy

O2pu oneself

p2 : water-gunmatch

transfer

Infer fuppernew

The latent function and fields of air-gun are inferred as fu1

new= (air-gun, fires, water)fi1

new= (child, outdoor)

Infer fu1new,fi1

new

2269


2256


2266


2265


2264


References and Citations

[1] Minami, K., Taura, T. and Tsumaya, A. (2010) A study on modeling of reasoning process considering latent

function, Design and Systems Division Conference of Japan Society of Mechanical Engineers, Tokyo,

Japan, 27-29 October.

[2] Yamamoto, E., Taura, T., Tsumaya, A. and Yamamoto, M. (2010) A Method for Function Dividing in

Conceptual Design by Focusing on Linguistic Hierarchal Relations, Journal of Computing and Information

Science in Engineering, vol. 10, 031004.

[3] Yoshikawa, H. (1981) General design theory and a CAD system, in Sata, T. and Warman, E.A(eds.)

(1981) Man-machine communication in CAD/CAM, Amsterdam, North-Holland.

2270


2257


2267


2266


2265


determining latent functions by focusing on the … if a latent function of “planting flowers”...

Documents