SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Systems BasicsSystems BasicsThroughout the Life Throughout the Life
CycleCycleJim Armstrong
SOFTWAREPRODUCTIVITYCONSORTIUM
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Engineering DefinedEngineering Defined
Problem
Technology
SolutionEngineering
“…the profession in which a knowledge of the mathematical and natural sciencesgained by study, experience, and practice is applied with judgement to developways to utilize, economically, the materials and forces of nature for the benefitof mankind.”
-Accreditation Board for Engineering and Technology
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Life Cycle Tasks ViewLife Cycle Tasks View
Systems Analysis
Systems Design
Design
Build/Integrate
Test
Use/Support
Produce
Test
Systems Spec
Product Specs
Design
Product
Changes
RiskReduction
Needs
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Cost of ChangesCost of Changes
123456789
10
Cos
t M
ultip
lier
Val
idat
ion
Tes
t
Inte
grat
e
Bui
ld
Allo
catio
n
Sys
tem
Req
uire
men
t
- Industry Studies
Systems Analysis
Systems Design
Design
Build/Integrate
Test
Use/Support
Produce
Test
Systems Spec
Product Specs
Design
Product
Needs
$?
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
NASA Cost ImpactNASA Cost Impact
Costs in Phase A and B as Percent of Development Cost
Fin
al C
ost
as
Exc
ess
Ove
rIn
itia
l P
has
e C
Co
mm
itm
ent
200
100
0
-200 15 30
Source: Presentation by Werner Gruhl,Office of the Comptroller, NASA HQ, 1985
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
EIA 632, May EIA 632, May 9898Operator
MaintainerPassenger
User or CustomerRequirements
AcquirerRequirements
Product
Other StakeholderRequirements
System TechnicalRequirements
25
14
16
16
20
26
15
27 2833
Missing Task
28
AssignedRequirements
14
26
17
29
1830
19
31Logical SolutionRepresentation
Physical SolutionRepresentation
SpecifiedRequirements
DesignSolution
“Source Req’s”?
32
21
Develop
Validate
Verify
Unknown
OtherSatkeholders
EnablingProducts
Ready
DerivedRequirements
17
19
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Systems Systems ActivitiesActivities
Functionality Requirements System Elements
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Requirements Requirements AnalysisAnalysis
Define
• Customer expectations
• Project, enterprise and external constraints
• Operation and maintenance concepts and scenarios
• Modes of operation
• System boundaries and interfaces
• Measures of Effectiveness
• Performance requirements
• Environments
- IEEE 1220
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Concept of Concept of OperationsOperations
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
System System BoundariesBoundaries
“Validated”SystemRequirement
Leve
l
Frequency
= Intelligible
Leve
l
Frequency
= Unintelligible
AdditionalRadio Loss
Operational UseRequirement
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Quality Functional Quality Functional DeploymentDeployment
• QFD - House of QualityHow's
Wha
t's
Comfortable ride
Wei
ght
Dam
peni
ngS
prin
g
Sea
t si
ze
Acc
elA
ccel
erat
ion
Spe
edP
riorit
y
Col
or
-
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Site Site VisitsVisits
• Understand customer environment
• Notice unstated requirements
— Unusual situations
— Requirements errors
— Environment
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Requirements Requirements QualitiesQualities
QUALITY A B C D E F G H I J K L M N
Completeness x x x x x x x x x x x
Consistency x x x x x x x x x x x
Correctness x x x
Feasible x x x
Formal x x x x
Minimal x x x x x
Modifiable/Maintainable x x x x x x x x
Right level of detail x x x x
Simplicity x x x x x x
Traceable x x x x x x
Unambiguous x x x x x x x x x
Verifiable/Testable x x x x x x x x
-Mar, 1994
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Requirements Requirements ReviewReview
• Motorola Iridium experience
— 600+ pages of system requirements
— 1,000 review hours
— Major and minor issues identified
— 40,000 hours saved!
• Continued effort on derived requirements
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Requirements Requirements IssuesIssues
• Verifiable?
— “The reliability of this system shall be the maximum achievable within the current state-of-the-art.” - Early MLS draft spec
• Achievable?
— “100% probability of detection and 0% false alarm rate” - Weather radar spec
• Resources available?
— “10,000 MTBF - Method X” - ILS draft spec
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Functional Functional AnalysisAnalysis
Define
• Functionality/behavior/data flow/control flow
• Timelines
• Functional interfaces
• Functional failure analysis
• Functional architecture
• States and transitions
- IEEE 1220
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Static Static ModelsModels
• Functional/Behavior/Data Flow Diagrams
SellTickets
ProvideInfo
MonitorSystem
CleanSystem
TransportGuests
LoadGuests
PrepareSystem
UnloadGuests
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Functional Interface Functional Interface OptionsOptions
F1
F2
F3
F4
F5
F6
F7
F8
AllocationAlternative 1
AllocationAlternative 2
= Function Output/Input
Functionsfromfunctionalanalysis
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Functional Functional InterfacesInterfaces
Launch
Orbit
Launch Orbit
Functional Interface/State Transition
Temp
Operate > -100
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Dynamic Dynamic ModelsModels
• Computerized
• Executable
• Demonstrate
— Interactions
— Timing
— Resources
— Alternative paths
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Model Model DepthDepth
• Shallow— Show basic performance— Depict interfaces— Simple design
• Deep— Understand complex interactions— Present driving design detail— Reveal technical issues— More complex design
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777 & 777 & StatemateStatemate
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Prototype Prototype ExampleExample
• Large airborne phased array - curved design
• Small prototype
— Large enough to validate math model
• “Final design may not be patch antenna.”
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
SynthesiSynthesiss
• Identify alternatives
• Define architecture
• Allocate functions
• Assess safety
• Define interfaces
• Develop models and prototypes
- IEEE 1220
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Strategy - Strategy - SBDSBD
Internal Component External Component
(SW)
(SW)
System Boundaries
• Schematic Block Diagram (SBD) depicts the physical architecture
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Integration & Integration & RequirementsRequirements
• Interface and boundaries defined
• Allocations made
• Interfaces recorded - Interface Control Documents
— Requirement
— Design
28 VDC
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Other Other ConsiderationsConsiderations
• Contracts
• Subcontracts
• Teams
• IPT’s
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Allocations – De Facto or PlannedAllocations – De Facto or Planned
Function Requirement Component
Or, how individual improvements can degrade system performance
Function Requirement Component
Destroy Target
Go to Target
Propel Bullets
Stabilize Bullets
Aim Gun
Control aircraft
Guide aircraft
Provide aerodynamics
Function Requirement Component
Destroy Target X% damage/hit
Go to Target +/- X degrees
Propel Bullets +/- X fps
+/- X bullets/second
+/- X degrees
Stabilize Bullets +/- X RPM
Aim Gun +/- degrees
Control aircraft +/- stability
Guide aircraft +/- control accuracy
Provide aerodynamics +/- stability & response
Function Requirement Component
Destroy Target X% damage/hit Bullets
Go to Target +/- X degrees Bullets
Propel Bullets +/- X fps
+/- X bullets/second
+/- X degrees
Gun
Stabilize Bullets +/- X RPM Gun
Aim Gun +/- degrees Mount/airframe
Control aircraft +/- stability Flight control
Guide aircraft +/- control accuracy Pilot
Provide aerodynamics +/- stability & response Airframe
Function Requirement Component
Destroy Target X% damage/hit Bullets
Go to Target +/- X degrees Bullets
Propel Bullets +/- X fps
+/- X bullets/second
+/- X degrees
Gun
Stabilize Bullets +/- X RPM Gun
Aim Gun +/- degrees Mount/airframe
Control aircraft +/- stability Flight control
Guide aircraft +/- control accuracy Pilot
Provide aerodynamics +/- stability & response Airframe
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Trade Trade StudiesStudies
• SPC Guide and Template
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Verification Verification MatrixMatrix
Requirement I A D T
3.1.1.7
3.1.2.9
3.1.3.2
3.2.1.1.5a
X
X
X
XX
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Verification Verification MethodsMethods
• Inspection
— Size, color, soldering, documentation…
• Analysis
— Hazardous situations, useful life…
• Demonstration
— Turn on sequence, part replacement….
• Test
— Performance, accuracies, interactions…
• Other
— Prior data, similarity...
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Design of ExperimentsDesign of Experiments
• Taguchi
Test Points
Test Volume
Solution Region
Parameter Z
Par
amet
er Y
Parameter X
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Design of ExperimentsDesign of Experiments
• Multiple alternative designsOptions
Prototype
1
2
3
4
5
6
A B C D E F
X
X
X X
X
XX
X XX
X X
X X
X
X
X
X
X X
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Additional Systems Additional Systems AnalysesAnalyses
• Logistic Support Analysis
• Survivability/vulnerability
• FMECA
• Systems Safety hazard analysis
• Reliability
• Human Factors
• EMI/EMP
• Lifecycle cost
• Linear programming optimization
• …..
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Life Cycle PhasesLife Cycle Phases
Systems Analysis
Systems Design
Design
Build/Integrate
Test
Use/Support
Produce
Test
Systems Spec
Product Specs
Design
Product
Needs
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Formal Formal ReviewsReviews
• Organize to elicit customer information
• Manage flow of information
• Know what you want to accomplish
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
Life Cycle ReviewsLife Cycle Reviews
Systems Analysis
Systems Design
Design
Build/Integrate
Test
Use/Support
Produce
Test
Systems Spec
Product Specs
Design
Product
Needs SRR
FDR SSR
PDR CDR
PCA
FCA
ACR
SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.
And in Proposal Writing!And in Proposal Writing!
• SE must be part of proposal effort
• Lack of or inadequate SE repeatedly disastrous
— Communications Network
— Air to Ground Missile