software productivity consortium copyright © 2003, software productivity consortium nfp, inc. all...

SOFTWAREPRODUCTIVITY CONSORTIUM Copyright © 2003, Software Productivity Consortium NFP, Inc. All rights reserved.

Systems BasicsSystems BasicsThroughout the Life Throughout the Life

CycleCycleJim Armstrong

SOFTWAREPRODUCTIVITYCONSORTIUM


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


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


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

$?


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


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


Systems Systems ActivitiesActivities

Functionality Requirements System Elements


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


Concept of Concept of OperationsOperations


System System BoundariesBoundaries

“Validated”SystemRequirement

Leve

l

Frequency

= Intelligible

Leve

l

Frequency

= Unintelligible

AdditionalRadio Loss

Operational UseRequirement


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

-


Site Site VisitsVisits

• Understand customer environment

• Notice unstated requirements

— Unusual situations

— Requirements errors

— Environment


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


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


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


Functional Functional AnalysisAnalysis

Define

• Functionality/behavior/data flow/control flow

• Timelines

• Functional interfaces

• Functional failure analysis

• Functional architecture

• States and transitions

- IEEE 1220


Static Static ModelsModels

• Functional/Behavior/Data Flow Diagrams

SellTickets

ProvideInfo

MonitorSystem

CleanSystem

TransportGuests

LoadGuests

PrepareSystem

UnloadGuests


Functional Interface Functional Interface OptionsOptions

F1

F2

F3

F4

F5

F6

F7

F8

AllocationAlternative 1

AllocationAlternative 2

= Function Output/Input

Functionsfromfunctionalanalysis


Functional Functional InterfacesInterfaces

Launch

Orbit

Launch Orbit

Functional Interface/State Transition

Temp

Operate > -100


Dynamic Dynamic ModelsModels

• Computerized

• Executable

• Demonstrate

— Interactions

— Timing

— Resources

— Alternative paths


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


777 & 777 & StatemateStatemate


Prototype Prototype ExampleExample

• Large airborne phased array - curved design

• Small prototype

— Large enough to validate math model

• “Final design may not be patch antenna.”


SynthesiSynthesiss

• Identify alternatives

• Define architecture

• Allocate functions

• Assess safety

• Define interfaces

• Develop models and prototypes

- IEEE 1220


Strategy - Strategy - SBDSBD

Internal Component External Component

(SW)

(SW)

System Boundaries

• Schematic Block Diagram (SBD) depicts the physical architecture


Integration & Integration & RequirementsRequirements

• Interface and boundaries defined

• Allocations made

• Interfaces recorded - Interface Control Documents

— Requirement

— Design

28 VDC


Other Other ConsiderationsConsiderations

• Contracts

• Subcontracts

• Teams

• IPT’s


Allocations – De Facto or PlannedAllocations – De Facto or Planned

Function Requirement Component

Or, how individual improvements can degrade system performance


Destroy Target

Go to Target

Propel Bullets

Stabilize Bullets

Aim Gun

Control aircraft

Guide aircraft

Provide aerodynamics


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


Destroy Target X% damage/hit Bullets

Go to Target +/- X degrees Bullets



+/- 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


Destroy Target X% damage/hit Bullets

Go to Target +/- X degrees Bullets



+/- 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


Trade Trade StudiesStudies

• SPC Guide and Template


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


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...


Design of ExperimentsDesign of Experiments

• Taguchi

Test Points

Test Volume

Solution Region

Parameter Z

Par

amet

er Y

Parameter X


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


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

• …..


Life Cycle PhasesLife Cycle Phases

Systems Analysis

Systems Design

Design

Build/Integrate

Test

Use/Support

Produce

Test

Systems Spec

Product Specs

Design

Product

Needs


Formal Formal ReviewsReviews

• Organize to elicit customer information

• Manage flow of information

• Know what you want to accomplish


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


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

software productivity consortium copyright © 2003, software productivity consortium nfp, inc. all...

Documents

requirements analysis

technology slide

assigned requirements

pages of system requirements

requirements issues

systems basics

cost of changes

customer environment