Various Types & Uses of FAST

P R O C E E D I N G S O F T H E SAVE C O N F E R E N C E — 1978

THE V A R I O U S TYPES A N D USES O F THE FAST D I A G R A M

Frank Wojciechowski

Manager, Product Cost Control

Loral Electronic Systems

Yonkers, New York

A B S T R A C T

In the past few years the use of FAST Diagramming has

expanded throughout the world. However, since it is

useful in so many d isc ip l ines, the development of FAST

is in a state of evolut ion. As with any new development,

each disciple finds new uses and variat ions, so that some

confusion arises when we try to communicate with this

new too l .

The Function Analysis System Technique (FAST) visual ly

presents the relationships of functions performed by a

product, s e r v i c e , or organizat ion, and identifies the

areas where functions have the greatest impact on cost .

FAST Diagramming is a process of thinking logical ly

about Function Analysis and it is this logic that is al I —

important as it is applied to the concepts of the various

d isc ip l ines .

In this paper, four different types of FAST Diagrams are suggested; an attempt is made to categorize them, their concepts are examined and an analysis of their use is made. Hopefully, this paper wi l l c lar i fy the apparent variations in the use of this versatile concept of F u n c tion Analysis and help us understand that although they differ in form, the underlying logic is basical ly the same.

But before I begin, I wish to point out that although the

names in the story are not f ict i t ious, they are by no

means a l l - i n c l u s i v e for we are relating a process of

evolution in which hundreds of people have part icipated.

The whole system, of course, started with Larry Miles

who 30 years ago asked the innocent sounding question,

"What does it d o ? " as the cornerstone of Value Ana lys is .

From this question, for the next 20 years , we struggled

with def ini t ion, c lassi f icat ion, and evaluation of

Functions. We philosophized and evolved techniques,

methods, and insights until today we are close to the

science of Function Ana lys is .

Type 1 Diagram - Bytheway

In 1967 Charles Bytheway conceived the original system

of FAST in an attempt to introduce logical thinking and

progression to the field of Function Ana lys is . In his

first paper "Basic Function Determination Technique" ,

he speaks of the Higher Aggregate Approach looking at

higher level functions, and finds that the basic functions

of lower level parts and assemblies come into existence

whenever a method to perform a higher level function is

chosen. This led him to the Determination Logic which

verified the Basic Function and made it possible to

identify higher level functions.

V A R I O U S U S E S O F " F A S T " D I A G R A M M I N G

First I wish to thank you for this opportunity to speak

about my favorite subject , Function Analys is , and its

latest evolutionary form: the FAST Diagram. Last y e a r ,

whi le glancing through the FAST diagrams in the S A V E

Proceedings, I was struck by the seemingly large variety

of diagrams not only in content and appl icat ion, but

also in their basic form and construction. In studying

them a bit deeper I soon real ized that we have actual ly

developed four different types of FAST diagrams. ' By

recal l ing the history of its development I tried to

classify the similarities and dif ferences. From history,

I placed some names on the various types. From the

names and the knowledge of the people, I generated a

story of its development which sheds some light on the

various purposes behind them, and from application of

the FAST Diagrams I wish to share with you the various

uses as I see them, of these four distinct types. I wi l l

therefore first present to you the story or "historical

nove l" of the development of the FAST Diagram and

then demonstrate the possible uses by presenting the

four types of diagrams on a single product.

In his ar t ic le "Fast Diagrams" in 1970, Mr. Bytheway points out that the questions used in developing a FAST Diagram are "subject oriented as well as creat ively oriented and provide (for the analyst) countless mot ivations for c rea t iv i ty" . The FAST procedure then is a technique using nine "thought-provoking questions" which are shown in Figure I.

HIGHER LEVEL -LOGIC

CRITICAL PATH

1. WHAT SUBJECT OR PROBLEM WOULD YOU LIKE TO DISCUSS?

2. WHAT ARE YOU REALLY TRYING TO DO WHEN VON «

3. WHAT HIGHER LEVEL FUNCTION HAS CAUSED 1 COME INTO BEING?

4. WHY IS IT NECESSARY TO 1 ?

_T0

5. HOW IS ^ ACTUALLY ACCOMPLISHED OR HOW IS IT PROPOSED TO BE ACCOMPLISHED?

6. DOES THE METHOD SELECTED TO 1 CAUSE ANY SUPPORTING FUNCTIONS TO COME INTO EXISTENCE?

BASIC FUNCTION DETERMINATION LOGIC

7. IF YOU DIDN'T HAVE T0_ .WOULD YOU STILL HAVE TO PERFORM THE OTHER FUNCTIONS LISTED?

. DO APPARENT DEPENDENT FUNCTIONS _ COME INTO EXISTENCE AS A RESULT OF THE SYSTEM CONCEIVED?

9. WHAT 0RWH0 ACTUALLY__t ?

•FILL IN WITH THE FUNCTION (A VERB AND A NOUN) YOU DESIRE TO DISCUSS.

Figure 1. Bytheway Questions

153


The answer to each question must be speci f ic and in

terms of a verb and a noun in such a way that the

answer discloses only the action required without

disclosing the method of performing that a c t i o n .

Mr. Bytheway points out "that since eight of the nine questions require a verb-noun answer and since each function describes an action without the method of • performing that ac t ion , the questions in and of themselves stimulate creat iv i ty . Therefore, during the development of a FAST Diagram (by this method), creat ivi ty is spontaneous. At each burst of creat iv i ty , the development of the FAST Diagram is set aside until the new idea or ideas are explored. . . .The value of a completed FAST Diagram is somewhat insignificant contrasted to the value of the thinking and creat ivi ty performed in developing a d iagram."

It is interesting to note that in a cover letter with this

paper Char les Bytheway s a i d , "Note that I have not

included the " W h e n ? " aspect since I'm not sure how

it fits into the approach we use to stimulate c r ea t i v i t y . "

A l s o , none of Bytheway's papers mention the use of

scope lines to limit the problem. While Mr . Bytheway

stresses the creat ive aspect of FAST Diagrams, he also

suggests that "it is a good way to organize our thinking.

The diagram lets us know if we are thinking l o g i c a l l y . "

He has told us that the FAST Diagram evolved as a

result of trying to ana lyze his method of th ink ing.

Type II - Ruggles

Around 1968 Wayne (Doc) Ruggles of Value Analysis I n c . ,

recognized the importance of FAST in structuring f u n c

tion ana lys is . However, Doc Ruggles, an exce l lent

teacher , had a problem - he conducted a one week

seminar and had to teach function analysis between

10:00 and 11:30 on Tuesday morning, which is not

sufficient time to explore the nine questions. As we

al l know, the seed of creativity is an intell igent mind

which is dissatisfied; therefore, taking Char l ie Bytheway's

"Cr i t ica l Path Logic" questions, "Why is it necessary

to (function) ? and "How is (function) actua l ly

a c c o m p l i s h e d ? " , Ruggles developed a simplified

version of the FAST Diagram with emphasis on the

Cr i t i ca l Path. A l l other remaining and identif iable

functions were a l located as follows (Figure 2 ) :

1. Below the cr i t ica l path are placed functions which occur at the same time or are caused by a function on the cr i t ica l path. (Answer the question When . )

2 . O n the right-hand side (above the l ine) are

p laced functions which occur "all the t ime" .

3 . On the top left -hand side are placed require

ments or specif ications (not functions) which you

wish to keep in mind while solving the problem.

HOW? WHY?

GROUND R U L E S

FUNCTIONS ' THAT HAPPEN "ALL THE TIME-

REQUIRED SECONDARY FUNCTION


FUNCTIONS THAT HAPPEN "AT THE SAME TIME" AND/OR "ARE CAUSED BY" SOME OTHER FUNCTION

154

Figure 2. Ruggles Fast Diagram

In addition to this structure Doc Ruggles also introduced

the "scope" lines which limit or provide boundaries for

the problem or study. The left scope line is placed

between the Basic Function and The Higher Order

Functions. Thus, the Basic Function is always found on

the immediate right of the" left scope l i ne . The right

scope line is p laced to the right of the last required

secondary function and excludes (to the right) a l l

functions outside the item or process being studied.

Doc Ruggles has given us a p rac t ica l , easy- to - teach technique, and therefore immediately useful . This technique yields a very simple but in-depth definition of a problem. The use of scope lines helps to bound the study to proper l imits, and the emphasis on the cr i t ica l path focuses the creat ive effort on the major required functions.

Type III - Park-Wojciechowski

In 1969 I was in the process of developing, with

Ted Fowler , Jim A l l i s and Harry Rosenfeld, an updated

training course for Xerox Corporation. S ince I was

generously a l located time and resources, I studied al l

the avai lable systems of FAST Diagramming in an

attempt to incorporate this new technique into a useful

methodology which could be communicated and taught

to others. The impressive part of the FAST Diagram

seemed to be the ease of structuring functions by use

of the How-Why L o g i c . The emphasis, therefore, was

placed on the strict use of this log ic . In discussions

with Richard J . Park of Chrysler Corporation we found

that he was thrusting in the same d i rect ion. Our

development of this method resulted in the following

general ized type of FAST Diagram (Figure 3):


HOW? I

I WHY?

HIGHER ORDER FUNCTION

BASIC FUNCTION


INPUT FUNCTION

I

Figure 3. Park-Wojciechowski Fast Diagram

1. Start with any function.

2 . Work both ways - using How and Why .

3 . Branch if two functions are needed to answer

the How and Why questions.

4. Draw scope lines as follows:

• On the left side - put the last function in the

problem that you have complete control of .

• On the right side - outside the scope are

functions which are input to the problem or

product. Without these functions performed

by someone else you cannot solve the problem.

For example, the e lect r ic company supplies

the power, someone else identifies the need;

the operator of a Xerox machines supplies

paper, dry ink, e t c .

5 . Make sure the How-Why logic is satisfied and drive a l l paths from one scope to the other.

From our point of v iew at that t ime, the advantage of this type of FAST Diagram is that it is easier to develop ini t ia l ly with the "expert" who has the problem. It is a translation technique al lowing the expert in his own discipl ine to clar i fy his definition of the problem and to communicate i t . This method immediately gives the following benefits:

I. Complete insight into the functions of a product or process with a good understanding of how they relate to each other - not just basic or supporting or unnecessary functions but how one function supports or creates the other and how a change in method in one function affects a l l functions l e a d ing to it (to the right of the chosen funct ion) .

2 . A shorthand diagram to explain the product,

process, or organization to people of other

discipl ines:

a . A Product FAST Diagram in development can be used to explain to a new engineer or support engineer (such as re l iab i l i ty , qual i ty , e t c . ) what is required and how it fits into the total product picture.

It can be used:

by Marketing to sell or promote product

features,

by Manufacturing to build and control

important function elements, and

by Management to a l locate resources and control the development process.

b. An Organization FAST Diagram provides a

simplified picture of the structure leading

to the organizational goals and the

detailed objectives leading to these goals .

It is an excel lent tool for focussing the

organizational elements of their functions,

and provides a criteria for measurement of

their accomplishments.

The addition of cost data (actual or estimated) to the FAST Diagram enhances the usefulness of this tool by specifying the function/cost re lat ion. It also highlights high cost areas, provides cost distribution information for decision making, and pin-points cost reduction opportunities.

This system is also useful for cost targeting for design-to-cost control in the following ways:

• B y using product cost information, the product cost can be controlled by updating with current estimates.

• B y using manpower or development cost da ta , the FAST Diagram is used for Program Contro l . In addit ion, by spreading out the FAST Diagram and adding a vertical time frame, a function/PERT control chart can be established, as well as manpower and resource al location for management and control .

• B y using other parameters al located to the functions a practical control diagram can be established for that parameter goa l , e . g . , an e lect r ica l power consumption for a machine to keep it below an established goal or to minimize power use .

1 5 5


Type IV Fowler-Snodgrass I. Determine basic function of product.

Another very useful form of FAST Diagrams has been

developed by my imcomparable co l league , Ted Fowler ,

together with the long-time practitioner of Basic

Function Analys is , Tom Snodgrass, at Value Standards

I n c . This method concentrates on the analysis of a

product from the customer's and/or user's point of v i e w .

It's a powerful tool for designing a new product for

competitive marketing, regaining a market position,

and understanding customer viewpoint and a c c e p t a n c e .

It has also been found to be an excel lent communication

tool between such varied disciplines as marketing,

sa les , engineering, and management.

The basic concept is that a product has a Basic Funct ion, which is the purpose of its ex is tence . In addit ion, it has many supporting functions which makes it accepted and desired by customers. Some of these functions are created by the nature of the product (assure dependabi l i ty , protect user) , and others by desires of customers (attract user, satisfy user) .

In this type of diagram, we have the Basic Function

section of the diagram with the supporting functions

grouped into four categories which branch to include

all the product's supporting functions. This grouping

and branching is essent ia l . This diagram wil l include

some secondary functions which have no v a l u e , but

this cannot be determined until the customer attitude

is determined.

The format of this type of FAST Diagram shown in

Figure 4 is constructed as follows:

HOW?

F U L F I L L NEED

BASIC FUNCTION

REQUIRED FUNCTION

W H Y ?

REQUIRED FUNCTION

ASSURE

DEPENDABILITY

SUPPORT FUNCTION

SUPPORT FUNCTION

ASSURE

CONVENIENCE

ENHANCE FUNCTIONS

PLEASE

SENSES

2 . Determine supporting functions to make product

acceptable to a customer from the customer's

viewpoint.

3 . Apply How and Why logic using the point of view of the user or users to determine functions needed to accomplish the Basic and Supporting functions.

4 . Al locate Product Cost to funct ion. *

5 . Survey the customers to determine customer

acceptance and al locate to funct ion.

D E M O N S T R A T I O N S U M M A R Y

In order to understand the inherent value of the variety

of techniques avai lable to us, we wi l l perform a function

analysis of a simple product using the various methods.

We have chosen to use Charles Bytheway's example of

the e lectr ic light bulb. Here is the item and notice the

individual parts (Figure 5 ) .

F I L A M E N T

LEAD- IN W I R E S

S T E M P R E S S

INSULATION

G L A S S B U L B

SUPPORT W I R E S

H E A T D E F L E C T I N G DISC

S T E M

BASE RIM

C E N T E R CONTACT

Figure 5. Light Bulb Assembly

Figure 4. Fowler-Snodgrass Diagram

Class ica l Function Analysis

In the Class ica l Milesian function ana lys is , the functions were defined in two words, listed and classif ied as to Basic and Secondary functions. The Basic Function was determined by choosing that function without which the product would not exist; in other words, the essential purpose of the product regardless of the design chosen -the essence of the product. There was strong focus on the use value although the secondary functions were further classif ied as:

•Necessary - those functions which were required to perform the Basic funct ion.

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P R O C E E D I N G S O F T H E S A V E C O N F E R E N C E — 1978

•Aes the t ic - those functions which were needed to make the product s e l l .

•Unnecessary - those functions which were not needed to perform the basic function and were created by a method of implementing other functions.

A standard method of performing this analysis on an

existing product was to determine the functions of a l l the

parts of subassemblies. Thus for the light bulb we have

the following definition and classif ication (Figure 6 ) .

PARTS FUNCTIONS BASIC SECONDARY

LIGHT BULB PRODUCE LIGHT X

BASE MOUNT LAMP CONDUCT CURRENT

X X

GLASS BULB EXCLUDE OXYGEN X

INSULATOR INSULATE CONDUCTORS X

FILAMENT CONVERT ENERGY PRODUCE LIGHT X

X

STEM SUPPORT FILAMENT INSULATE CONDUCTORS

X X

SUPPORT WIRES CONDUCT CURRENT X

LEAD-IN WIRES CONDUCT CURRENT X

CENTER CONTACT CONDUCT CURRENT X

THE BASIC FUNCTION OF PRODUCE LIGHT HAS VALUE AND THE EMPHASIS WAS TO MINIMIZE THE COST OF THE SECONDARY FUNCTIONS.

Figure 6. Classical Function Classification

Not ice that we have developed eight functions of which

only the Basic Function has value and the thrust was to

put a l l the dollars into the basic function - but the

classif ication was based on experience or guessing.

Type I Example

Charles Bytheway used this example to demonstrate the use of FAST Diagrams. His FAST Diagram for the light bulb is as follows (Figure 7 ) .

Here, Ladies and Gentlemen we see a real breakthrough for the first time in the history of Function Analysis we didn't have to guess - we could f inal ly explain the interaction of Functions log ica l l y . We could learn from each other and we could teach others.

Type II Example

But, as mentioned before. Doc Ruggles had a problem and those nine questions were part of the obstac le . Therefore he used a simpler, more cdnc ise , structure for the FAST Diagram which for the light bulb example would probably look as shown in Figure 8 .

The method of developing this diagram is to consider

yourself as the lamp and what do I (the lamp) d o ? Thus

we have such functions as Receive E lect r ic Energy and

Position Parts. Note also the visual aspect of the c o m

pleteness of the boundaries of the problem, the focus

H O W ? 05

R E D U C E

BASE

T E M P E R A T U R E

10

D E F L E C T

HEAT

05

R E D U C E

BASE

T E M P E R A T U R E

10

D E F L E C T

HEAT

W H Y ?

/ /

/ /

/ /

/ I

U6

POSITION

14

POSITION 16

POSITION

BUTTON F I L A M E N T \

\

SUPPORT

WIRES

16

POSITION

BUTTON

N.

15 N MOUNT

LAMP

M E C H A N I C A L L Y

01

PROVIDE

LUMINOUS

E N E R G Y

U2 03 IM PRODUCE C O N V E R T L IGHT E N E R G Y F I L A M E N T

U7 11 17 m ( » SUPPLY CONDUCT

CONNECT MOUNT

V POWER C U R R E N T L E A D - I N LAMP

w C U R R E N T

WIRES E L E C T R I C A L L Y

\ \

\ \

\ \

\ \

\

PATH OF C R I T I C A L FUNCTIONS

PATH OF SUPPORTING FUNCTIONS

Figure 7. Bytheway Light Bulb Diagram

1 5 7

08

P R E V E N T

F ILAMENT

OXIDATION

12

E X C L U D E

O X Y G E N

08

P R E V E N T

F ILAMENT

OXIDATION

12

E X C L U D E

O X Y G E N

09

P R E V E N T

F ILAMENT

EVAPORATION

13

INSERT

I N E R T

GAS

09

P R E V E N T

F ILAMENT

EVAPORATION

13

INSERT

I N E R T

GAS

18

I N S U L A T E

CONDUCTORS

19 21

CONSTRAIN PROVIDE

G A S E S A I R - T I G H T

S E A L I N G


HOW?

L I M I T T E M P E R A T U R E I R I S E

" ~ l 1 F I T I N T O J | S T A N D A R D |

^ P R O V I D E ^ 1 1000 |

^ L U M E N S

P R O V I D E LUMINOUS E N E R G V

R E C E I V E E L E C T R I C A L E N E R G Y

1 P R O D U C E I

1 H E A T I

I 1

Figure 8. Ruggles Light Bulb Diagram

on the major essential functions defined by the cr i t ica l path with the lesser status of the secondary functions. This type of diagram provides the essential functions, (cal led Required Secondary Functions) which must be performed to accomplish the Basic Function regardless of the design chosen. In this way it is a powerful tool for development of original concepts and new product designs. It would be more useful to develop a f luorescent light to replace the light bulb but less useful in redesigning the filament support.

Type III Example

The Park-Woj ciechowski method of developing and using a FAST Diagram is more detai led in that it c o n tains more functions but returns to the simplicity of the How-Why l o g i c . In fact it does not use the W h e n ? approach at a l l but tries to force a l l functions into How-Why from one scope line to the other. The light bulb diagram might look as shown in Figure 9.

PRODUCE LUMINOUS ENERGV PR00UCE UNIFORM ENERGY

PROVI OE SURFACE AREA 1 PROVIDE JUR-TIGHT COMTAIHER

— SCOPE Of PROBLEM -

Figure 9. Park-Wojciechowski Light Bulb Diagram •

NOTE: Changing the Basic Function from Produce Light to Produce Uniform Light is not significant in this example but was included to indicate how this produces another set of functions - Diffuse Light and Frost Bulb.

This type of diagram seems more complicated but is a l l -inclusive from Basic Function on the left to implementation hardware on the right. It also visually presents the dependence of functions on each other. For example , if we did not have to Supply Filament we would e l i m i nate al l the functions coming into it from the right, e t c . The addition of cost data on each individual function box as well as cumulative along each path gives further visibi l i ty to the problem.

Type IV Example

By far the most inclusive form of FAST Diagram is the Fowler-Snodgrass type . This customer-oriented approach helps to eliminate some of the natural bias included in any product which includes what the engineer wants to design, what the production man l ikes to bu i ld , what marketing thinks is easy to s e l l , and what many people bel ieve the "Corporate Image" should b e . Continuing with our simple example, the light bulb FAST Diagram would appear as shown in Figure 10 to the various customers and users.

J H E A T j |T F I L A M E N T |

J FRO! ] " | S U L E

Figure 10. Fowler-Snodgrass Light Bulb Diagram

Not ice that the basic function is related to the customer and user. I mention customer/user in the context of the person who buys and uses the product in a l l its varied aspects. For example, if we consider a coffee vending machine we have:

• Operator - Person who puts in money and pushes buttons and removes f i l led c u p .

158


•Operator - Person who f i l ls machine with goods.

• Repairman - Locates problem and fixes machine when it breaks down.

•Customer - Buyer or lessee who places machine in his establishment.

• Buyer - Person who buys machine from manufacture.

The multiple points of view could be complicated so we return to our simple example. You wil l notice that certain functions, such as Assure Dependability and Satisfy User, are considered from the users position in that you want a satisfied customer and repeat business. Other functions, such as Attract Buyer are related to offering something to help with the initial s a l e . As you can perce ive , this multifaceted approach gives an i n -depth understanding. One advantage of this type of FAST is that on any item al l groups wil l develop ident i cal diagrams.

A N A L Y S I S O F " F A S T " D I A G R A M

The function of the FAST Diagram is to present graph

ica l ly the inter-relation of functions. The util ity of

this interrelation depends on the need or purpose for

which it is developed - the al l important Point of V i e w .

We must use the type of FAST Diagram which is a d v a n

tageous to our purpose.

The classic approach of Function Analysis is to Def ine , C lass i fy , and Evaluate Functions. Therefore, the use of the FAST Diagram in Function Analysis is to help define and classify the functions. It is used in this way to define a problem (meaning product, se rv ice , procedure, e t c . ) and as such takes some guidance from the problem.

Let us illustrate using the already developed FAST Diagrams. If you were in the Research and Develop-* ment Department, and your problem was to develop a new light bu lb , the Type II diagram, with its emphasis on Produce Light , Convert Energy functions would be most useful since it forces you to focus on the general functions regardless of design approach which is where the breakthrough wil l be found.

If, however, you were in the R&D department of the

Filament Lamp Division of the company and your prob

lem was to develop a new filament type light bulb or

drastical ly improve the existing product, the Type I

FAST Diagram would be helpful since it emphasizes the

step-by-step creativity and justification of functions

leading to a more thorough understanding of design

concepts.

If, however, you were a Design and Development

Engineer or a Manufacturing Engineer in the Filament

Lamp Division and your problem was to improve a product and reduce its cost , then the Type III Diagram would be more helpfu l . This diagram forces a complete detailed understanding of the product and diagramati -ca l l y interrelates the functions so that the effects of changes can be quickly analyzed and their impact on other functions determined.

If, however, you had a new product to develop to

increase your market penetration or improve a market

posit ion, the use of Type IV diagram is indicated.

In a similar manner the use of these FAST Diagrams in analysis of Organizations or Object ives would vary with the level at which the study is conducted and the amount of operating detail needed at that l e v e l . For example, a President and staff would use a Type II Diagram, department heads a Type I, and the line and middle management would most l ikely use Type I I I .

Classifying the types of FAST Diagrams by levels may be an over-simplif ication and it might be more appropriate to think of these types as varying in emphasis or thrust toward a problem solution. Cer ta in ly , in a very complex problem, such as in the design of a machine with thousands of unique parts, or in a conglomerate industrial organizat ion, we must start with high level functions and a simplified diagram. This leads us to defining problem areas which then should be expanded into their own FAST Diagrams. Choosing a FAST Diagram might be compared to going to a ball game. We need one map or set of directions to find the bal lpark, another to find a parking p l a c e , and a third to find our seat .

As mentioned by Bytheway, the importance of the FAST

Diagram is in the thinking, c lar i f ica t ion , and discussion

which goes into developing it and not in the final

diagram. The Bytheway diagram with its excursions into

creat ivi ty as each portion is developed may never be

completed. Not ice that in giving an example of

Type II diagram, I mention it might look l ike this since

in general each diagram wil l look different depending

on the thinking of the people developing i t , and after

its completion only the participants wil l understand it

and the details that went into i t . The Type IV diagram

comes closer to a good grouping technique and most

groups wil l develop identical diagrams.

A l l these diagrams are evolutionary and each has its own

strengths and weaknesses. We have not yet developed a

genera l i zed , uniform method. We must remember however,

that each of these FAST Diagrams are complete in them

selves and useful tools for a speci f ic purpose. In the

final analysis al l forms are useful since they force the

definition and analysis of function and a Va lue S p e c i a l

ist should develop the skil l of as many FAST Diagrams

as possible to add to his repertoire.

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Various Types & Uses of FAST

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