Advanced Software Engineering

AdvancedSoftwareEngineering

Lecture1:

IntroductiontoSoftwareEngineering

Prof.HaroldLiu

Content

 Basicconceptofsoftwareengineering

 Computer‐basedsystemsengineering

 SoftwareProcess

 Basicelementsofsoftwareprojectmanagement

1.WhatisSoftware？

 Software=program+data+document

 Customizedsoftware

 Genericsoftware,Shrink‐wrappedsoftware

 Embeddedsoftware

 Safety‐criticalsoftware

 COTS(CommercialOff‐the‐Shelf)

 “Iwillcreateasoftwaretoupdatethedatabase”.

(somesoftware,apieceofsoftware,asoftwaresystem)

 Categorizedbyitsfunctionalities,scale/size,operational

method,requiredreliability,etc.

2.WhatisSoftwareEngineering?

 Fall,1968,NATOTechnicalCommitteeconvenednearly50

first‐classprogrammers,computerscientistsandindustry

giants,discusshowtocopewith"softwarecrisis".FritzBauer

atthemeetingforthefirsttimeputforwardthe"Software

Engineering"concept.

 Theestablishmentanduseofsound engineeringprinciplesin

ordertoobtaineconomicallysoftwarethatisreliableand

worksefficientlyonrealmachines.” ‐‐‐ FritzBauer,1968

 IEEEDefinition:Softwareengineeringis

(1)thesystematic,standardized,measurablemethodisapplied

tosoftwaredevelopment,operationandmaintenanceofthe

process,theupcomingengineeringappliedtosoftware

developmentprocessthinking

(2)researchinto(1)

 Softwareengineeringgoals:low‐cost,high‐quality,on‐time

delivery

EssentialCharacteristicsofSoftwareEngineering

 Concernedabouttheconstructionoflargeprograms

 Howtocontrolthecomplexity

 Constantlychangingsoftwarerequirements

 Aimedatimprovingtheefficiencyofsoftware

development

 Teamworkisthekeytothesuccessfulimplementationof

softwareengineering

 Softwaremusteffectivelysupportitsusers

 Culturalbackgrounddifferenceforsoftwareproduct

creation.

5.WhatisSoftwareProcess？

 Softwareprocessisthedevelopmentofsoftwareproductsfora

groupofactivitiesandtheirresults.

 Allsoftwareprocesscontainsfourbasicactivities:Software

description,softwaredevelopment,softwarevalidationand

softwareevolution.

 Differentsoftwareprocessesorganizedindifferentwaysinthese

fouractivities,whichmayaffecttheresultsoftheprogressof

events.

 Differentbodiesmaybeusedtoproducethesametypeof

processproducts.

Benefits

 Asoftwareprocessdefinesthatinordertoachievethegoals,what

peopleneedinwhatwayatwhattimewhatkindofworkdone (Goal,

Who,When,How,What)

 ForCustomer,User,Developer,Manager,awidelyapplicable

softwareprocessallowsallstakeholderstobetterunderstandtheir

roleandothers’ role,aswhattodoatwhattime.

 Promotetheintegrationprocesstoobtainthe"bestsoftware

process.“

 Makethecompany'sinternaltrainingstandardized.

 Duetotherepeatabilityofthesoftwareprocess,usefulforthe

developmentschedulearrangementsandcostestimates.

6.WhatisSoftwareProcessModel？

 ModelsandModeling

 Softwareprocessmodelisbuiltfromaparticular

perspectiveonthenatureofthesoftwareprocess

description.

 Softwareprocessmodelincludesavarietyof

activitiesthatareconstitutingthesoftwareprocess,

softwareproducts,aswellasallstakeholders

 Fromadifferentperspectiveofthesoftwareprocess

described,yougetadifferenttypeofprocessmodels.They

are:

 Workflowmodel:Describesthesequenceofaseriesof

activities,inputs,outputsandinter‐dependencie.Herewe

refer“Activities”ashumanactivity.

 Datastreamoractivitymodel:thesoftwareprocessdescribed

asasetofactivities,eachofwhichcompletescertaindata

conversion.Thereferredlevelofactivityinthismodelis

belowtheworkflowmodel.

 Role/actionmodel:Describesthedifferentrolesinvolvedin

thesoftwareprocessanditsresponsibleactivities.

Paradigm,Methodology

 WaterfallModel

 WaterfallModelwithMaintenanceCircle

 WaterfallModelwithPrototyping

 SpiralModel

 VModel

 PhasedDevelopmentModel

 IncrementalandIterativeModel

 RationalUnifiedProcess

7.Costsanddistributions

 Softwarecostsdependontheadoptedsoftware

processandthetypeofsoftwarebeingdeveloped.

 Generaldistributionof costs:

Description:Design:Development:Integrationand

Test(15:25:20:40)%

 High‐demandsoftwaresystems:integration/testing

50:50%

 Fromsoftwareevolution

 Frommaintenance

 Web‐basede‐commercesystem

8.Methodologies

 StructuredMethod,byDeMarco,1978,YourdonE.

andConstantineL.et.al.

 JacksonSystemDevelopment,1983

 Object‐OrientedMethod,byBooch,1994;

Rumbaugh etal,1991Æ DesignPatterns

UML(UnifiedModelingLanguage)

• In1994,OOprinciplehasbeenthroughouttheentire

softwarelifecycle,italreadyhasanimpacton50+

OOA&Dmethods.

• UMLisakindofmodelinglanguageforvisualization,

decription,structuringanddocumentation,mainlyfor

theanalysisanddesignphaseofsystemmodeling.

UML2.0

1994

Booch Method

Rumbaugh OMT

Coad/Yourdon

FireSmith

Method

JacobsonOOSE

……

1995.10

UnifiedMethod0.8

1996.6UML0.9

12companiesincl

RationalformupUML

organization,andthen

UML1.0.

In1997.1,submittedto

OMG

1997.11.4,OMG

adoptedUML1.1

In2002,UML2.0is

published

RUP

 ByIBMRational

 Highlights

 Use‐casedriven（functionality）

 architecture‐centric（design）

 Iterativeandincrementaldevelopments（implementation）

 UsingUMLandothertools

TendencyforChangewhenUsingOO

Paradigm(Jacobsonetal.1995)

HighFunctionality

HighInterfacewiththeoutsideworld

MediumSequencesofbehavior

MediumPassiveobject’sattribute

LowLong‐livedinformationstructures

LowObjectsderivedfromtheapplication

ProbabilityforchangeCharacteristicofSWproduct/project

9.WhatisCASE？

 Computer‐AidedSoftwareEngineering(CASE)

 Abunchoftoolstosupportthesoftware

enegnieeringprocess

 Lower‐endtools:togeneratecodes

 High‐endtools

todrawenterprisemodelandapplication

requirementsspecifications

10.ProblemsofSoftwareEngineering

 Legacysystems

 Changingrequirements

 Delivery

 …

 Systemcomplexityanddetails(Marsprobefailure)

 Technologicaluncertainty(andinturntheunderstandingof

developers)

 Communicationbarriers

 Requirementuncertainty

 Constantchangesleadtothesoftwaredegradation

 Artificialandthemarketrisk

 Costs,reliability,productivity,reusabilityproblems

11.Moralresponsibility

 Professionalethics isveryimportant

 Alwayskeepemployerandclients’ informationconfidential

 Realisticallyexpresshis/herabilitytowork,donotacceptwork

beyondthecapability.

 Shouldbeawareofthelawsrelatedtopatents,copyrights,etc.

 Avoidcomputermisuse.

 ACM/IEEE/BCSandotherorganizationsissuedaCodeof

ProfessionalConductandEthics(involvingonlybasicmoral

behavior)

Content

 BasicConceptofSoftwareEngineering

 Computer‐basedSystemEngineering

 SoftwareProcess

 Basicelementsofsoftwareprojectmanagement

1.SystemOverallCharacteristics

 Functional

 Non‐functional:reliability,security,privacy,safety

issues

 Whatrelatesthesystemreliability：

 HW

 SW

 Operational

2.SystemandItsSurvivingEnvironment

 Environmentisamust‐have

 Environmentwillaffectthesystem'sfunctionalityand

performance.

 Intheenvironmentthereexisitaseriesofinteractionswith

othersystems.Thus,theenvironmentcanbetreatedasa

stand‐alonesystem.

 Systemsengineermustunderstandthesystemenvironment

 Inmanycases,thesystemistochangetheenvironment.

 Asystemcanbeaffectedbyenvironmentalchanges,andsucheffects

maybedifficulttoestimate.

3.SystemModeling

 Systemmodelingdescribesthecomponentsofthesystem

andtheirrelationships(systemarchitecture)

 Systemarchitectureisgenerallydescribedinblockdiagram.

 Subsystems

 Functionalcomponentscanbedividedintosixcategories:

 Sensors:Gatherinformationfromtheenvironment.

 Actuators:incurtheenvironmentalchanges

 Computingcomponents:givenaninput,performcalculationsand

produceoutput.

 Communications

 Scheduling:coordinationofoperationsbetweencomponents.

 Interface

4.ProcessforSysEngineering

Req Def

Sys Design

Component dev

Sys integration

Sys installation

Sys evolvement

Sun-set

 Subsystemdevelopment:

 Parallel

 Frequentmodificationsbeyondthescopeofa

subsystemmayhappen(HW?SW?)

 Systemintegrationbyincrementalprocess

 Hardtoestimatetheexacttimingfora

subsystem

 Accurateerror‐positioning(whichsubsystem

causesthefailure?)toreducethe

disagreementofdifferentsubcontractors

5.BuyingSoftwares

 Whatisthebestwayofpurchase?Whoisthebest

provider?

 Beforepurchasing,system‐leveldescriptions and

architecturaldesignmustbedone,tomakesure

which“subsystem” needstobepurchased.

 Whoisthecontractor,andwhoisthesub‐contractor.

Client

Contractor

Subcon2Subcon1

Subcon3

Content

 BasicConceptofSoftwareEngineering

 Computer‐basedSystemEngineering

 SoftwareProcess

 Basicelementsofsoftwareprojectmanagement

1.SoftwareProcessModel

 Anabstractrepresentationofthesoftwareprocess

 Inpractice,multiplemodelsareused.

 Fourkindsofmodels

 Life‐cyclemodel(waterfall)

 Evolutionarydevelopmentmodel

 Formalmethods

 Reuse‐orienteddevelopmentmodel (OO)

Waterfall

• Waterfall

• ClassicLifeCycleModel

• LinearSequentialModel

Prob Def

Req Analy

High‐levelDesign

Low‐leveldesign

coding

testing

maintenance

 Dependenciesbetweenany

twosubsequentstages

 Deferdevelopmentafter

designs

 Toensurequality

Pros

 Developmentprocessisessentiallyinalinear

sequence,manageable

 Basedon"clearandcomprehensive

requirements“,thus abletoachievesatisfactory

results

Costofchanges

Afterrelease

TheImpactofChanges

Definition

Development

1.5~6x

••••••

60~100x

Proj Plan

Req Analy

High‐levelDesign

Low‐levelDesign

Coding

Testing

Maintenance

Circle

Plan

Req Analysis

Operations

Justification

coding

design

WaterfallModel

withMaintenanceCircle

EvolutionDevelopmentModel

 Basedontheinitialrequirement,firstdevelopa 

prototypeforclients.Then,basedonthefeedback,

continuouslyimprovethesystemuntil satisfactory.

 Requirementscanbeconstantlychanged.

 Twowaysofdoingit:

 Workingwithclientstogetheruntildelivery

 Prototypeistounderstandtheclients’ needs.

 Problemsofevolutiondevprocess：

 Whereis“process”?

 Noclearsystemarchitecture

 Inpractice,weusethecombinedmodel:

 WaterfallModelwithPrototyping

 VModel

 PhasedDevelopmentModel

 IncrementalandIterativeModel

 SpiralModel

Maintenance

Req Analysis

High‐levelDesign

Low‐leveldesign

Codingandunittesting

Integrationtesting

Delivery

Prototyping

Systemtesting

Validate

Verify

WaterfallModel

withPrototyping

V‐Model

PhasedDevelopmentModel

TheIncrementalandIterativeModel

IncrementalDevelopment

IterativeDevelopment

create

format

create

formatedit

create

More

styles

Easy

quick

create

More

styles

Paste

easy

create

styles

Paste

clumsy

ExamplesinAgile

BenefitsofIncrementalDevelopment

 Candelivertheproductwithmainfunctionalities

withinshortperiodoftime

 Graduallyincreasetheprovidedfunctionalities,so

thatusershaveampletimetolearnandadaptto

thenewproject

SpiralModel

BenefitsofSpiral Model

 Softwarere‐use

 Softwarequalityisimportantfordev

 Reduceunnecessary/surplustesting

 Nodifferencebetweensoftwaremaintenanceand

development

RationalUnifiedProcess

 Iterativeandincrementaldevelopment

 Use‐casedriven

ProjectManagement

Environment

BusinessModeling

Implementation

Test

Analysis&Design

Preliminary

Iteration(s)

Iter.

Phases

ProcessWorkflows

Iterations

SupportingWorkflows

Iter.

#n+1

Iter.

#n+2

Iter.

#m+1

Deployment

Configuration&ChangeMgmt

Requirements

Elaboration TransitionInception Construction

Inaniteration,you

walkthroughall

workflows

FormalMethods

 Similartothewaterfallmodel,but

 Requirementdescriptionsarehighlyreplyon

mathematics(e.g.,notations,equations...)

 Aseriesoftransformationsleadtoexecutable

programs

 Cleanroom ProcessbyIBM

OperationalSpecificationModel

Operational

Specification

(problem‐

oriented)

Transformed

Specification

(implementation

–oriented)

TEST

Executeand

Revise

System

Requirements

(sometimesinformal

orincomplete)

Delivered

System

TransformationalModel

Transformn

Formal

Specification

problem‐oriented

Transform2

TEST

Comparewith

requirements;

Updateasneeded

System

Requirements

(sometimesinformal

orincom

lete)

Delivered

System

Transform1

FormalDevelopmentRecord

Sequenceof

transformations

Plusrationaleforthem

2.SoftwareDescriptions

 Feasibilitystudyreport

 Requirementanalysis

 Requirementdescriptions

 Requirementvalidations

3.SoftwareDesigns

 Architecturaldesign

 Subsystemabstractdescription

 Interfacedesign

 Componentdesign

 Datastructuredesign

 Algorithmdesign

4.SoftwareValidation

 Unittesting

 Functionalmoduletesting

 Subsystemtesting

 Systemtesting

 Deliverytesting(α、β、λ)

5.SoftwareEvolution

 Definition:Softwareevolutionisthetermusedinsoftware

engineering (specificallysoftwaremaintenance)toreferto

theprocessofdevelopingsoftware initially,thenrepeatedly

updatingitforvariousreasons.

 Thenatureofsoftwareflexibilitydeterminesthatsoftware

evolutionisamust

 AvoidexpensiveHWmodifications

 Canberegardedasanintegratedprocessbetweendevand

maintenance

6.SoftwareAutomation

 CASE

 Limitations

 Byessence,softwareengineeringisacreativeactivity

 Softwareprocessemphasizestheteamwork

Content

 BasicConceptofSoftwareEngineering

 Computer‐basedSystemEngineering

 SoftwareProcess

 Basicelementsofsoftwareprojectmanagement

SoftwareProjectManagement

 cleardistinctionwithotherprojectmanagement.

 SoftwarePMneedstotakeavarietyofdifferenttasks,oneof

themostimportantactivitiesareprojectplanning,estimating

costsandschedulecontrol.

 Projectmilestoneissththatisexpectedandplanned.When

reachingamilestone,PMneedstoreporttheprogresstothe

mangementboard.

 Inordertoeffectivelytrack/controltheprojectprogress,PM

canuseavarietyofcharts/diagrams.

 Shouldidentifyandassesstheprojectrisk,determinethe

likelihoodoftheserisksandconsequences.

1.WhattoManage?

 Peoplemanagement

 Costestimations

 Qualitycontrol

 Processimprovement

 Softwareconfigurationmanagement

2.ProjectPlanning

 Essenceistoestimatethepotentialrisksandadopt

effectivemethodtosolvetheproblems

 Contents:

 Projectplan

 Qualityplan

 Configurationmanagementplan

 Maintenanceplan

 Trainingplan

 …

3.ResourcePlanning

 PMneedstoestimatetheamountof“resources” to

useinordertocompletetheproject,andorganize

theseresourcesinanoptimalway.Theyare:

 HW

 SW

 Costs

 Space

 People

 Time

 …

4.RiskManagement

 Identifythepotentialrisksandmaketheplan,tomaximally

lowertheirimpacttotheproject

 Threetypesofrisks

 Product：thathaveimpactonthesoftwarequalityand

performance

 Project：thathaveimpactontheprojectprogressand

resources

 Business：thathaveimpactonthesoftwarecompany

and/orclients

 Howtomanagetherisks?

 Identification,analysis,plan,andmonitoring

PotentialSoftwareRisks

BizPeer

competition

BizTechchange

SomeCASEtoolsareveryexpensiveproductPoorCASEperf

OverbudgetProject&

product

Underestimate

thesystemscale

Project&

product

Description

delay

inevitableprojectChangeofreq

e.g.,orderedHWisnotdeliveredprojectLackofHW

projectRe‐org

ExperiencedstaffsprojectStaffquit

Descriptions

TypeRisks

RiskAnalysis

NegligibleMediumCodes generated by CASE tools are

inefficient

TolerableHighUnderestimate the software size

Tolerable MediumLack of training

TolerableMediumClients not sure of the req

TolerableHighCASE tools cannot be used

SignificantHighUnderestimate the dev efforts (time)

SignificantMediumDatabase problem

SignificantHighRe-org

SignificantMediumReq change leads to re-design

SignificantMediumDefect on re-useable components

SignificantMediumStaff report sickness at important stage

SignificantHighLack of qualified staff

SignificantLowFinancial problems, to cut the budget

consequencePossibilityRisks

CausesofSoftwareRisks

ProgressisdelayedUnderestimatethesoftware

size,timing,defects

plan

Toomuchchanges,clientcomplaintsChange,misunderstanding,

communications

req

UsingtoolsarenoteasyCASE toolstools

Re‐org,financialproblemsOrg

Tasksarenotassignedproperly,team

internalchaos

Recruitment,staffchanging

jobs,training

Staff

HW/SWdeliverydelay,exposestoo

manytechproblems

DB,re‐useablecomponents,or

COTS

Tech

ExamplesPotentialrisksType

RiskManagementStrategies

PurposehighperformanceDBDBperformance

Draftareporttothemgmtteam,explaintheimpacttotheprojectRe‐org

Evaluatetheimpactofchange,increasethetraceabilityofthedev

process

Req change

PurposereliablecomponentsComponentdefect

Re‐formthedevteam,flexibletaskassignment,efficient

communications.

Staffsickness

Tellclientsthepotentialrisks/delaythismaycauserecruitment

Draftareporttothemgmtteam,explaintheimpacttotheprojectFinancialproblems

StrategiesRisks