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Transcript of Crawley BP Lec p2 v2 061207
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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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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
Product/system boundary
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
Product/system boundary
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
Whole product system
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
Product/system boundary
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
Product/system boundary
Whole product 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
Product/system boundary
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
Product/system boundary
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
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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
Insert scanned image of cannon camera system
product/system boundary
External function at the interface: produce + digital image
External function at the interface: produce + analog image
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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
Insert scanned image of cannon camera system
Product/system boundary
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
Product/system boundary
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
Product/system boundary
GroundInterface
Vout
R 1
R 2- 5V
+5V
Vin
-+
+ Inputinterface
Op Amp
Delivered and Internal Function Amp
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 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
Product/system boundary
Delivered and Internal Function - Bubblesort
What is the value related operand andstates?What is the externally delivered function?
What are the internal functions?How are they mapped to form?
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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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