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Massachusetts Institute of Technology Ed Crawley 2007

System ArchitectureIAP Lecture 2

Ed CrawleyJanuary 11, 2007

Rev 2.0

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Reflections on Definitions?

System

Complex

ValueProduct

Principle/Method/Tool

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Architecture

Consists of: Function

Related by Concept To Form

Form

F

u n c t i o n

Concept

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Form - Reflections?

What is the form of simple systems?

How did you express the decompositional view?

How did you represent the graphical structuralview?

How did you represent the list like structural view?

What do the lines in the graphical view, or connections in the list view represent? Is it form?

Did you identify classes of structural relations?

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Form Topics

Representing form and structure

Whole product system and use context

Boundaries and InterfacesAttributes and states

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7/80Massachusetts Institute of Technology Ed Crawley 2007

Representations of Form

Form can be represented by: Words (in natural language - nouns) Code Illustrations, schematics, drawings Each discipline has developed shorthand for

representing their discipline specific form

But the form is the actual suggested physical/informationalembodiment.

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Duality of Physical and Informational Form

Physical form can always be represented byinformational form (e.g. a building and a drawing of abuilding)

Informational form must always be stored or encoded inphysical form (data in a CD, thought in neurons, poetryin print)

So there is a duality of the physical and informationalworld (styled after the duality of particles and waves)

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Classes of Structural Connections

Connections that are strictly descriptions of form : Relative spatial location or topology (e.g. above, is next

to, is aligned with, is within, overlaps with, etc.) whichrefers to previous arranging process Information about assembly/implementation (e.g.

connected to, bolted to, compiled with, etc.) whichrefers to previous assembling/implementing process

Connections that are description of function while operating (still to be discussed)

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Spatial/Topological Structure - Whistle

Bump Cavity

Hole

Ramp StepChannel

Product/system boundary

Bump

Cavitywall

Hole

Ramp

Step

Channel

Touches

Is a boundary of

Touches

Is aboundary of

Touches

Is a boundary

Is aligned with

Is aboundary of

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Defined: A structural link is the symbol that represents abinary relationship between two objects.

There is also a backward direction relation.

Usually it is only necessary to show one, and the other is implicit.

OPM Object-Object Structural Links

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Structural Link Examples

Capacitor Resistor Is connected to

Chair TableIs under

Wheels Axelare bolted to

Disk Bladescontacts25

Data ArrayIs stored inn

Spatial (under)

Topological (within)

Topological (touching)

Implementation

Implementation

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Spacial/Topological Structure - Whistle -List

Is boundedby

Is bounded bytouchesCavity

Is aboundary of

Is aligned withIs aboundary of

Step

Is aboundary of

Is alignedwith

Is aboundary of

Hole

touchesIs boundedby

Is bounded bytouchesRamp

touchestouchesChannel

touchesBump

CavityStepHoleRampChannelBump

N-squared matrix representation gives a list-like representation of connectivity (read from left row-wise)Symmetric (with transformation like surrounds to within, is aboundary of to is bounded by)Is non-causal - no sense of anything happening before anything else

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Implementation Structure - Whistle

Bump Cavity

Hole

Ramp StepChannel


Bump

Cavitywall

Hole

Ramp

Step

Channel

Mech.integral

Mech.integral

Mech.integral

Mech.integral

Mech.integral

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Implementation Structure - Whistle - List

Mech.Integral

Mech.Integral

Cavity

Mech.integral

Mech. integralMech.integral

Step

Hole

Mech.integral

Mech.integral

Mech.integral

Ramp

Mech.integral

Mech.integral

Channel

Mech.integral

Bump

CavityStepHoleRampChannelBump

N-squared matrix representation gives a list-like representation of connectivity (read from left row-wise)Symmetric, non-causal - no sense of anything happening beforeanything elseSpatial and implementation structure can be combined by showingone in the upper and one in the lower diagonal

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Issues RaisedHow do you identify form independent of function?How do you define the atomic part level? For hardware?For software?Can you decompose an integral part? Can a part be asystem? Can the features of a part be elements?How do you represent the structural interconnections of the elements, as opposed to their membership in asystem?N occurrences of an element - count once or N times?The class or each instance?

Connectors and interface elements - count as a separateelement - or combined with other elements?Are there important elements lost in implementation?Are there elements important to delivering value other than the product?

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Form of Product/System - Questions

What is the product system?What are its principle elements?What is its formal structure (i.e. the structure of form)?

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The Whole Product SystemWe usually architect form which is both a product and a system,

and which we designate the product/systemOften for the product/system to deliver value, it must be joined andsupported by other supporting systemsMost often, one of the other objects in the supporting system is theoperator, the intelligent (usually human) agent who actuallyoperates the system when it is usedTogether, the product/system, plus these other supporting systems,constitute the whole product system

?SupportingSystem 1Supporting

System 2 Operator Supporting

System 3Supporting

System 4

Whole Product System


Whole product system

Wh l d t t

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Bump

Cavitywall

Hole

Ramp

Step

Channel

Product/system

boundary

Bump

Cavitywall

Hole

Ramp

StepChannel

Operator

Star

Ring

ExternalAir

Whistle

610

Whole Product System -Whistle


The whistle onlyrequires an operator and the air to work

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Use Context

??SupportingSystem 1Supporting

System 2 Operator Supporting

System 3Supporting

System 4

Whole Product System

Use Context

Use Context

System 4

Use Context

System 1

Use Context

System 2

Use Context

System 3


Whole product systemUse context

The whole product system fits within a use context, which included theobjects normally present when the whole product operates, but notnecessary for it to deliver valueThe product/system usually interfaces with all of the objects in the wholeproduct system, but not with the objects in the use contextThe whole product system is usually use independent, while the usecontext is context dependentThe use context informs the function of the product/system

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Use Context Informs Design

The use context informs the requirements for and thedesign of the product/system

For example: Whistle use context: sporting event, toys, Olympic stadium? Op amp use context: lab bench, consumer audio, spacecraft?

The architect must have a view of three layers of the form:The product/system, the whole product and use context

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Boundaries and Interfaces

The product/system is separated from other supportingsystems and the operand by a boundaryThe boundary is vital to the definition of architecture,because it defines: What you architect, eventually deliver and are

responsible for What is fixed or constrained at the boundariesEverything that crosses a boundary must be facilitatedby an interfaceIt is good practice to draw the system boundary clearlyon any product/system representation, and identifyinterfaces explicitly

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Op Amp - Whole Product System

Amp

GroundInterface

R 2R 1Op Amp

-5 VInterface

- inputInterface

+ InputInterface

+ 5 VInterface

OutputcircuitGround

Inputcircuit

Power supply

WholeAmp System



There will be an interface to other elements of the whole product system

Therefore knowledge of these elements informs interface control

OutputInterface

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Amp - Whole Product and Boundaries

Ground

R 2

R 1

- 5 Vinterface

Outputinterface

- Input

interface

+ 5 Vinterface

Power supply

Inputcircuit

Outputcircuit


What are the boundaries?

What are the interfaces?

GroundInterface

Vout

R 1

R 2- 5V

+5V

Vin

-+

+ Input

interface

Op Amp

What is the whole product system

What is the use context?

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Amp - WholeProduct SystemBoundary and

Interfaces

lower diagonal spacial/topological, upper implementation

r e s

i t o r

1

r e s

i s t o r

2

o p a m p

+ i n p u

t i n t e r f a c e

- i n p u

t i n t e r f a c e

o u t p u

t i n t e r f a c e

g r o u n

d i n t e r f a c e

- 5 V

i n t e r f a c e

+ 5 V i n t e r f a c e

i n p u

t c i r c u

i t

o u t p u

t c i r c u

i t

p o w e r s u p p

l y

g r o u n

d

resitor 1 x e eresistor 2 x e eop amp x ei ei ei ei ei+input interface t x e-input interface t t t xoutput interface t t x eground interface t x e

-5 V interface t x e+5 V interface t x einput circuit t x eoutput circuit t x epower supply t t x eground t t t t x

t = touching, tangentb = boundaryw = within, s = surroundingov = overlappingda = at a specified distance or angular allignment

m = mechanical connected (pressing, bolted, bonded, etc.)e = electrical connected (soldered, etc.)c = compilation with

no second symbol implies connector of some sorti as second symbol implies integral

ImplementationInterfaces

Spatial Interfaces

In the matrixrepresentation,the boundary isbetween rowsand columnsInterfaces areclearly identified

in the block off diagonals

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Whole Product System - Code BubblesortProcedure bubblesort ( List array, number length_of_array)

for i=1 to length_of_arrayfor j=1 to length_of_array - i

if array[ j ] > array [ j+1 ] thenexchange_contents (array, j)

end if end of j loop

end of i loopreturn array

End of procedure

Procedure exchange_contents( List array, number j)

temporary = array [ j+1 ]array[ j+1 ] = array [ j ]

array[ j ] = temporaryreturn array


What are the boundaries?

What are the interfaces?

What is the whole product system

What is the use context?

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The structuralinterfaces insoftware determinesequence andnesting, andcompilation

Example assumes thatprocedureexchange_contents isseparately compiled andcalled

Bubblesort -Whole ProductBoundary and

Interfaces

lower diagonal spacial/topologicalupper implementation

p r o c s t a

t e

I l o o p

i n s t

j l o o p

i n s t

i f i n s t

t e m p

i n s t

a ( j + 1 ) i n s t

a ( j ) i n s t

r e t u r n s t a

t e

proc state x c c c cI loop inst f x c c c

j loop inst fw x c cif inst fw x ctemp inst fw x c ca(j+1) inst w f x ca(j) inst w f x

return state f x

t = touching, tangentb = boundaryw = within, s = surroundingov = overlappingda = at a specified distance or angular allignmentf = follows in sequence, l = leads in sequence

m = mechanical connected (pressing, bolted, bonded, etc.)e = electrical connected (soldered, etc.)c = compilation with

no second symbol implies connector of some sort

i as second symbol implies integral

h l

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Static Graphical User Interface - Whole

Product?

What are the boundaries?What are the interfaces?

What is the whole product systemWhat is the use context?

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Form of Whole Product - Questions

What is the product system? Its elements? Its formalstructure?What are the supporting systems?What is the whole product system?What is the use context?

What are the boundaries?What are the interfaces?

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Characterization

Characterization/Exhibition The relation between an object

and its features or attributes Some attributes are states

O

A

Decomposes toHas attribute of

O

A

c h a r a c t e r i z e s

ex h i b i t s

Skateboard

Brand Length Velocity

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State

Defined: State is a situation in which the objectcan exist for some positive duration of time (andimplicitly can or will change)The combination of all the states describes thepossible configuration of the system throughoutthe operational time.The states can be shown with the object, or alternatively within an attribute object.

Skateboard Skateboard

Stopped Rolling

Velocity

Stopped Rolling

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Summary - Form

The physical/informational embodiment which exists, or hasthe potential to exist

Objects + Structure (of form)

Is a system attribute, created by the architect

Product/system form combines with other supporting

systems (with which it interfaces at the boundary) to form thewhole product system that creates value

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Architecture

Consists of: Function

Related by Concept To Form

Form

F u n c t i o n

Concept

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Function Topics

FunctionEmergenceProcess + OperandExternal functionInternal function

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Function - Defined

The activities, operations and transformations that cause, create or contribute to performance(i.e. meeting goals)

The actions for which a thing exists or isemployed

Is a product/system attribute

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Function - Described

Is conceived by the architect

Must be conceived so that goals can be achieved

Is what the system eventually does, the activities

and transformations which emerge as sub-function aggregate

Should initially be stated in solution neutrallanguage

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Function - Other views:

Function is what the system doesForm is what the system is [Otto]

Function is the relationship between inputs andoutputs, independent of form [Otto]

Process is a transformation (creation or change)

applied to one or more objects in the system [Dori]

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Function is Associate with Form

Change voltage proportional to current

Change voltage proportional to charge

React translation forces

Carry moment and shear

Conditionally transfer control

Assign a value

if array[ j ] > array [ j+1 ] then

temporary = array [ j+1 ]

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Emergence

As elements of form are brought together, new functionemergesUnlike form, which simply aggregates, functions do notcombine in any linear way - it is often difficult or impossible, a priori , to predict the emergent function

In design, the expected function may appear, may fail toappear, or an unintended function may appear It is exactly this property of emergence that givessystems their power- definition of system: A set of interrelated elements that perform a function,

whose functionality is greater than the sum of theparts

F i E F A bl

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Function Emerges as Form Assembles

Attenuate high frequency

Increase force

Amplify low frequency signal

Regulate shaft speed

Vin Vout

F in Fout

Vin

Vout

Emergent function depends onelements and structure

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Function Emerges as Form Assembles

Procedure bubblesort ( List array, number length_of_array)for i=1 to length_of_array

for j=1 to length_of_array - i

if array[ j ] > array [ j+1 ] then

temporary = array [ j+1 ]array[ j+1 ] = array [ j ]array[ j ] = temporary

end if

end of j loopend of i loop

return arrayEnd of procedure

ExchangeContents

Conditionally ExchangeContents

Sort fromsmall tolarge

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Form - Function Sequence

Reverseengineering,

Bottom up

design,Design

knowledgecapture

Mapping

Formdefinition

Functiondefinition

Mapping

Conceptualdesign

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Design vs. Reverse Engineering

In (conventional, top down) design, you know thefunctions (and presumably the goals) and try tocreate the form to deliver the functionIn reverse engineering, you know the form, and aretrying to infer the function (and presumably eventuallythe goals)In bottom up design, you build elements and discover what emerges as they come together

In design knowledge capture, you record the functionalong with the design of form

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Exercise: Reverse Engineering of Function

This is an exercise to demonstrate reverse engineeringof function of objects with which you are not personallyfamiliar What is the function of: A notebook? A pen? A glass? A set of instructions? An object I give you?

Examine the object, and describe its form

Try to discern and describe its functionFunction and form are completely separate attributes.

Even when form is evident, function is not easily inferred without a working knowledge of operation, operand and whole product system.

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Function = Process + OperandNote that function consists of the action or transformation + the operand, an object which is actedon, or transformed: Change voltage React force

Amplify signal Regulate shaft speed Contain liquid Lay down ink Stop an operator

Count circles

The action is called a processThe object that is acted upon is called the operand

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The Operand

Operand is the object which is acted upon by theprocess, which may be created, destroyed, or altered: Image is captured Signal is amplified Array is sorted

You often do not supply the operand, and there may bemore than one operand to consider The double arrow is the generic link, called effectingA single headed arrow can be used to representproducing or consuming

ProcessingOperand

Function

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Value Related Operand

The product/system always operates on one or

several operandsIt is the change in an attribute of one of an operandsthat is associated with the delivered value of theproduct system

Because of its importance to value, it is useful tospecially designate this value related operand

Value rela ted Operand

Whole product System

Product/ System

Supporting Systems

Other Operands

610

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Camera - Value Related Operand?

Insert scanned image of cannon camera system

product/system boundary

Whats the value related operand ?

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E t ll D li d F ti

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Externally Delivered Function


product/system boundary

External function at the interface: produce + digital image

External function at the interface: produce + analog image

610

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Form Enables Process

Enablers of a process is an object that must be presentfor that process to occur, but does not change as aresult of the occurrence of the processExamples: Capturing by a digital camera Amplifying with an operational amplifier Sorting with bubblesort routine

The arrow with the circular end represents andenabler, which can be an instrument (non-human) or anagent (human)

ProcessingInstrument

Object

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Three Core Ideas

Operand - an element of form external to the productsystem, whose change is related to benefit and thereforevalueProcess - the transformation or change in the operandForm - the instrument that executes the transformation(and attracts cost!) and consists of elements plusstructure

Wouldnt it be nice if we had a semantically exact way of representing these 3 core ideasHow can we do with conventional representations?

610

Semantically Exact Representation with

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Semantically Exact Representation withOPM

Architecture is made up of operands + processes(functions) plus instrument object (form)Examples: Image is captured by digital camera Low frequency signal is amplified with an operational amplifier Tone is created by whistle Array is sorted by bublesort routine

ProcessingInstrument

ObjectOperand

Function Form

610

Value Related State Representation with

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Value Related State Representation withOPM

Architecture delivers value when the externally deliveredoperand changes its state through the action of theprocesses enabled by instrument object (form)Examples: Image (none to existing) is captured by digital camera Low frequency signal (low amplitude to higher amplitude) is

amplified with an operational amplifier Tone (none to existing) is created by whistle Array (unsorted to sorted) is sorted by bubblesort routine

Processing InstrumentObject

Operand

Value Related Function Form

Value states

Existing Desired

l b d l

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A Tool - Object Process Modeling

Object: that which has the potential

of stable, unconditional existence for some positive duration of time.Form is the sum of objects and their structure

Process: the pattern of transformation applied to one or more objects. Processes change anobject or its attribute.

Function emerges from processesacting on operandsAll links between objects andprocesses have precise semantics

Objects

Processes

OPM P Li k

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OPM Process Links

P changes O (from state A to B).

P affects O

P yields or creates O

P consumes or destroys O

O is an agent of P (agent)

O is and instrument of P

P occurs if O is in state A

P1 invokes P2 directly

TransportingPersonHere

There

TransportingPerson

TransportingEntropy

TransportingEnergy

TransportingOperator

TransportingSkateboard

PurchasingMoneyEnough

None

Purchasing Transporting

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Value

Value is benefit at cost Simple metrics are benefit/cost, benefit - cost, etc. Sometimes more complex metrics

Benefit is worth, importance, utility as judged by asubjective observer (the beneficiary)

Another view:

Value: how various stakeholders find particular worth, utility, benefit, or reward in exchange for their respective contributions to the enterprise [Murman,et al. LEV p178]

V l d A hi

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Value and ArchitectureValue is benefit at cost

Benefit is driven by functionexternally delivered across theinterface

Cost is driven by the design of theform - parts attract cost

The relationship of function to form istherefore the relationship of benefitto cost

A good architecture delivers benefit at competitive cost

Form

F u n

c t i o n

Concept B e n e f i t

Cost

V l Q i ?

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Value - Questions?

What is the value related operand?What are the value related states that change?What is the externally delivered function?

E t ll D li d F ti E g f

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Externally Delivered Function Emerges fromInternal Function

System function which emerges at the highest level isthe externally delivered function which usually acts onthe operand

Example: amplify low frequency signalSystems have internal functions, which combine toproduce the emergent externally delivered function Example: amplify , change voltage ...

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Externally Delivered and Internal Function

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Externally Delivered and Internal Function



External function at the interface: produce + digital image

External function at the interface: produce + analog image

Restrain +camera

Capture + digital image

Power +camera

Store + digital image

Interface +Camera andcomputer

610

I t l F ti Q ti ?

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Internal Functions - Questions?

What are the principle internal functions?How are the internal functions mapped to elementsof form?How do these combine to produce the emergent

externally delivered value related function?

Deli ered and Internal F nction Whistle

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Delivered and Internal Function - Whistle

Bump Cavity

Hole

Ramp StepChannel


BumpCavity

wall

Hole

Ramp

StepChannel

Touches

Is a boundary of

Touches

Is aboundary of

Touches

Is a boundary

Is aligned with

Is aboundary of

What is the value related operand andstates?What is the externally delivered function?

What are the internal functions?How are they mapped to form?

Delivered and Internal Function - Amp

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Ground

R 2

R 1

- 5 Vinterface

Outputinterface

- Inputinterface

+ 5 Vinterface

Power supply

Inputcircuit

Outputcircuit


GroundInterface

Vout

R 1

R 2- 5V

+5V

Vin

-+

+ Inputinterface

Op Amp

Delivered and Internal Function Amp



Delivered and Internal Function Bubblesort

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Procedure bubblesort ( List array, number length_of_array)for i=1 to length_of_array;

for j=1 to length_of_array - i;if array[ j ] > array [ j+1 ] then

exchange_content (array[ j ], array [ j+1 ])end if

end of j loop

end of i loopreturn arrayEnd of procedure

Procedure exchange_contents( List array, number i, number j)

temporary = array [ j+1 ]array[ j+1 ] = array [ j ]array[ j ] = temporary

return array


Delivered and Internal Function - Bubblesort



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Summary - Function

Function is the activity, operations, transformations thatcreate or contribute to performance - it is operand + process

Function is enabled by form, and emerges as form isassembled

Externally function delivered to the operand is linked to thebenefit of a product/system

Function is a system attribute, conceived by the architect

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Reference PDP?

Why would you have a formalized PDP?What are the essential features of the Ulrich andEppinger model?

What are the key limiting assumptions?How does this compare with the PDP in your enterprise?

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Goals of a Structured PDP

Customer-focused productsCompetitive product designsTeam coordination

Reduce time to introductionReduce cost of the designFacilitate group consensusExplicit decision processCreate archival recordCustomizable methods

Ref: Ulrich and Eppinger

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PDP Org

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In the SMALL v. In the LARGE

SIMPLECountable interfacesParts identifiable

STATICGoals & resources

constant

SMALLTeam at a table

COMPLEXVery many interfacesParts abstracted

EVOLVINGGoals & resources

changing

LARGEBig team

v.

v.

v.

Product:

Process:

Organization:

Other Factors: clean slate vs. reuse of legacy components; singleproduct vs. platform; collocated vs. distributed team; team in

enterprise vs. supplier involvement

g

Product

Process

S R f PDP

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Summary - Reference PDP

A useful reference for in-the-small consumer focusedmechanically based productsA tool to reduce ambiguity by defining roles andprocesses

Adaptable to a variety of contexts, staying within the keyassumptions

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