软件体系结构考试.docx

软件体系结构考试.docx

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软件体系结构考试

CS6075FinalTake-HomeExamAnswers

9:

00am–3:

00pm,May19,2013

1.（8%）Answerthefollowingquestionsaboutthebigideaofsoftwarearchitectureinsoftwareengineering:

a）Whataretheprincipalinsightsfromthedisciplineofbuilding（conventional）architecturethatareapplicabletotheconstructionofsoftwaresystems?

Ans:

Weallliveinthem.

Weknowhowtheyarebuilt:

Requirements,Design（blueprints）,Construction,Use.

Satisfactionofcustomers’needs.

Specializationoflabor.

Multipleperspectivesofthefinalproduct.

Intermediatepointswhereplansandprogressarereviewed.

Architectureisdifferentfrom,butlinkedwiththeproduct/structure.

Propertiesofstructuresareinducedbythedesignofthearchitecture.

Thearchitecthasadistinctiveroleandcharacter.

Processisnotasimportantasarchitecture.

Designandresultingqualitiesareattheforefront.

Processisameans,notanend.

Architecturehasmaturedovertimeintoadiscipline.

Architecturalstylesassetsofconstraints.

Stylesalsoaswiderangeofsolutions,techniquesandpalettesofcompatiblematerials,colors,andsizes.

Adistinctiveroleandcharacterinaproject.

Verybroadtraining.

Amassesandleveragesextensiveexperience.

Akeensenseofaesthetics.

Deepunderstandingofthedomain:

Propertiesofstructures,materials,andenvironmentsandNeedsofcustomers.

Evenfirst-rateprogrammingskillsareinsufficientforthecreationofcomplexsoftwareapplications.

b）Lists5ormoredifferencesbetweentasksofasoftwarearchitectandabuildingarchitect.Explainyouranswer.

Ans:

Thenatureofsoftwareisdifferentfromthatofbuildingarchitecture.Theyaredifferentthingsindifferentareas.

Softwareismuchmoremalleablethanphysicalmaterials.Whenabuildingisbuilt,itcan’tbechanged.However,softwarecanbeupdatedandrebuilt.

Thetwo“constructionindustries”areverydifferent.Thetwowholeindustrieshavenosimilarity.

Softwaredeploymenthasnocounterpartinbuildingarchitecture.

Softwareisamachine;abuildingisnot.

Softwarecanbeeasilycopied;abuildingisnot.

2.（8%）Answerthefollowingquestionsaboutthesoftwarearchitecturecentricapproachinsoftwarelifecycle:

a）Thearchitecture-centricapproachemphasizesthatsoftwarearchitectureisartifact,notsoftwaredevelopmentphase.Explainthatifweonlyconsidersoftwarearchitectureasadevelopmentphase,whattheroleofsoftwarearchitectureisinsoftwarelifecycle.Explainthatifweconsidersoftwarearchitectureasdevelopmentartifact,whattheroleofsoftwarearchitectureisinsoftwarelifecycle.

Ans:

Asaphase:

Treatingarchitectureasaphasedeniesitsfoundationalroleinsoftwaredevelopment.Itismorethan“high-leveldesign”.Architectureisalsorepresented,e.g.,byobjectcode,sourcecode,...

Asaartifact:

Theroleisinthewholesoftwarelifecycle,containingRequirements,Design,Implementation,AnalysisandTesting,EvolutionandDevelopmentProcess.

Requirements:

TraditionalSEsuggestsrequirementsanalysisshouldremainunsulliedbyanyconsiderationforadesign.However,withoutreferencetoexistingarchitecturesitbecomesdifficulttoassesspracticality,schedules,orcosts.Inbuildingarchitecturewetalkaboutspecificrooms……ratherthantheabstractconcept“meansforprovidingshelter”.Inengineeringnewproductscomefromtheobservationofexistingsolutionandtheirlimitations.Existingdesignsandarchitecturesprovidethesolutionvocabulary.Ourunderstandingofwhatworksnow,andhowitworks,affectsourwantsandperceivedneeds.Theinsightsfromourexperienceswithexistingsystemshelpsusimaginewhatmightworkandenablesustoassessdevelopmenttimeandcosts.Requirementsanalysisandconsiderationofdesignmustbepursuedatthesametime.

Design:

Traditionaldesignphasesuggeststranslatingtherequirementsintoalgorithms,soaprogrammercanimplementthem.Architecture-centricdesignstakeholderissuesdecisionaboutuseofCOTScomponentoverarchingstyleandstructurepackageandprimaryclassstructuredeploymentissuespostimplementation/deploymentissues.

Implementation:

Theobjectiveistocreatemachine-executablesourcecode.Thatcodeshouldbefaithfultothearchitecture.Alternatively,itmayadaptthearchitecture.Howmuchadaptationisallowed?

Architecturally-relevantvs.-unimportantadaptations.Itmustfullydevelopalloutstandingdetailsoftheapplication

AnalysisandTesting:

Analysisandtestingareactivitiesundertakentoassessthequalitiesofanartifact.Theearlieranerrorisdetectedandcorrectedthelowertheaggregatecost.Rigorousrepresentationsarerequiredforanalysis,soprecisequestionscanbeaskedandanswered.

Evolution:

Motivation.Evaluationorassessment.DesignandchoiceofapproachActionincludespreparationforthenextroundofadaptation

DevelopmentProcess:

Traditionalsoftwareprocessdiscussionsmaketheprocessactivitiesthefocalpoint.Inarchitecture-centricsoftwareengineeringtheproductbecomesthefocalpoint.Nosingle“right”softwareprocessforarchitecture-centricsoftwareengineeringexists.

b）Explainthat,intermsofunittestsofasoftwaresystem,basedonthesystem’ssoftwarearchitecturemodels,whatblack-boxtestcasescanbedesigned?

Whatwhite-boxtestcasescanbedesigned?

Ans:

3.（20%）Answerthefollowingquestionsabouttheconceptsofsoftwarearchitecture:

a）Give2ormorereasonsthatpotentiallycauseasoftwaresystem’sprescriptiveanddescriptivearchitecturesmismatch?

Ans:

Asystem’sprescriptivearchitecturecapturesthedesigndecisionsmadepriortothesystem’sconstruction.Itistheas-conceivedoras-intendedarchitecture

Asystem’sdescriptivearchitecturedescribeshowthesystemhasbeenbuiltItistheas-implementedoras-realizedarchitecture

Reasons:

Thenatureofthecomponents

Thenatureoftheconnection

Theglobalnatureofthearchitecture

Constructionprocesses

b）Useonesentencetoexplaineachofthefollowingelementsofasoftwaresystem’sarchitecture:

component,connector,andconfiguration.

Ans:

Component:

encapsulateprocessinganddatainasystem’sarchitecture

Connector:

anarchitecturalbuildingblocktaskedwitheffectingandregulatinginteractionsamongcomponents

Configuration:

asetofspecificassociationsbetweenthecomponentsandconnectorsofasoftwaresystem’sarchitecture

c）Softwarearchitectureisasetofprincipledecisionsonasoftwaresystemin4aspects:

structure,behavior,interaction,andnon-functionalproperties.Youareaskedtodesignasoftwaresystemforausertomanagehiscontactlistwiththefollowingfunctionality:

addanewcontact,deleteacontact,updateacontact,searchacontact,andviewacontact.ThesoftwarearchitecturemustbebasedonMVCarchitecturalpattern.

·DrawaUMLclassdiagram,withclassesandtheirrelationships,toshowthestructureofthesystemarchitecture.Foreachclassinthediagram,justgiveitsnameandoperationswithoutsignature.

·DrawaUMLsequencediagramtoshowthecollaborativeobjectbehaviorsthatimplementoneoftheaboveoperations.

·Describeyourchoiceofconnectorsthatimplementcommunicationsbetweensystemcomponents.

·Giveoneexamplerequirednon-functionalpropertyofthesystem.

Ans:

Classdiagram

Sequencediagram

4.（12%）Answerthefollowingquestionsaboutsoftwarearchitecturalstyles:

a）Useonesentencetoexplaineachofthefollowingcategoriesofarchitecturalstyles:

layered,dataflow,sharedmemory,interpreter,implicitinvocation,andpeer-to-peer.

Ans:

layered:

Hierarchicalsystemorganization.“Multi-levelclient-server”.Eachlayerexposesaninterface（API）tobeusedbyabovelayers

dataflow:

Separateprogramsareexecutedinorder;dataispassedasanaggregatefromoneprogramtothenext.

sharedmemory:

memorythatmaybesimultaneouslyaccessedbymultipleprogramswithanintenttoprovidecommunicationamongthemoravoidredundantcopies

Interpreter:

Interpreterparsesandexecutesinputcommands,updatingthestatemaintainedbytheinterpreter

implicitinvocation:

atermusedbysomeauthorsforastyleofsoftwarearchitectureinwhichasystemisstructuredaroundeventhandling,usingaformofcallback.

peer-to-peer:

adistributedapplicationarchitecturethatpartitionstasksorworkloadsbetweenpeers.

b）Whatisincommonbetweenvirtualmachinestyleandinterpreterstyle?

Whatisthedeferencebetweenthetwo?

Explainyouranswer.

Ans:

Avirtualmachine（VM）isasoftwareimplementedabstractionoftheunderlyinghardware,whichispresentedtotheapplicationlayerofthesystem.Virtualmachinesmaybebasedonspecificationsofahypotheticalcomputeroremulatethecomputerarchitectureandfunctionsofarealworldcomputer.

Interpreterparsesandexecutesinputcommands,updatingthestatemaintainedbytheinterpreter

Components:

Commandinterpreter,program/interpreterstate,userinterface.

Connectors:

Typicallyverycloselyboundwithdirectprocedurecallsandsharedstate.

Highlydynamicbehaviorpossible,wherethesetofcommandsisdynamicallymodified.Systemarchitecturemayremainconstantwhilenewcapabilitiesarecreatedbaseduponexistingprimitives.

Superbforend-userprogrammability;supportsdynamicallychangingsetofcapabilities

LispandScheme

c）Whenyouuseanobject-orientedprogramminglanguage,suchasJava,todevelopasoftwaresystem,thesystemimplicitlyappliesobject-orientedarchitecturalstyle.Applyinganyadditionalarchitecturalstyleresultsinthatthesystemarchitecturewillbebasedonacombinationoftwoormorestyles.Useanexampletosh