keypoint.docx

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keypoint

PPT1

Whatissoftware?

Computerprogramsandassociateddocumentationsuchasrequirements,designmodelsandusermanuals.

Softwareproductsmaybedevelopedforaparticularcustomerormaybedevelopedforageneralmarket.

Newsoftwarecanbecreatedbydevelopingnewprograms,configuringgenericsoftwaresystemsorreusingexistingsoftware.

Whatissoftwareengineering?

Softwareengineeringisanengineeringdisciplinethatisconcernedwithallaspectsofsoftwareproduction.

WhatisthedifferencebetweenSEandCS?

Computerscienceisconcernedwiththeoryandfundamentals;softwareengineeringisconcernedwiththepracticalitiesofdevelopinganddeliveringusefulsoftware.

Whatissoftwareprocess?

Asetofactivitieswhosegoalisthedevelopmentorevolutionofsoftware.

Genericactivitiesinallsoftwareprocessesare:

–Specification-whatthesystemshoulddoanditsdevelopmentconstraints

–Development-productionofthesoftwaresystem

–Validation-checkingthatthesoftwareiswhatthecustomerwants

–Evolution-changingthesoftwareinresponsetochangingdemands.

Whatissoftwareprocessmodel?

²Asimplifiedrepresentationofasoftwareprocess,presentedfromaspecificperspective.

²Examplesofprocessperspectivesare

³Workflowperspective-sequenceofactivities;

³Data-flowperspective-informationflow;

³Role/actionperspective-whodoeswhat.

WhatistheCASE?

²CASEmeansComputerAidedSoftwareEngineering.

²Softwaresystemsthatareintendedtoprovideautomatedsupportforsoftwareprocessactivities.

²CASEsystemsareoftenusedformethodsupport.

Upper–lower

Whatisthedifferencebetweensoftwareengineeringandsystemengineering?

SEisconcernedwithallaspectsofthedevelopmentandevolutionofcomplexsystemwheresoftwareplaysamajorrole.

Systemengineeringisconcernedwithhardwaredevelopment,policyandprocessandprocessdesignandsystemdeploymentaswellassoftwareengineering

PPT2

1.

•Softwareprocessesaretheactivitiesinvolvedinproducingandevolvingasoftwaresystem.

•Softwareprocessmodelsareabstractrepresentationsoftheseprocesses.

•Generalactivitiesarespecification,designandimplementation,validationandevolution.

•Genericprocessmodelsdescribetheorganisationofsoftwareprocesses.Examplesincludethewaterfallmodel,evolutionarydevelopmentandcomponent-basedsoftwareengineering.

2.

•Iterativeprocessmodelsdescribethesoftwareprocessasacycleofactivities.

•Requirementsengineeringistheprocessofdevelopingasoftwarespecification.

•Designandimplementationprocessestransformthespecificationtoanexecutableprogram.

•Validationinvolvescheckingthatthesystemmeetstoitsspecificationanduserneeds.

3.

•Evolutionisconcernedwithmodifyingthesystemafteritisinuse.

+Exploratorydevelopment

–Objectiveistoworkwithcustomersandtoevolveafinalsystemfromaninitialoutlinespecification.Shouldstartwithwell-understoodrequirementsandaddnewfeaturesasproposedbythecustomer.

+Throw-awayprototyping

–Objectiveistounderstandthesystemrequirements.Shouldstartwithpoorlyunderstoodrequirementstoclarifywhatisreallyneeded.

•TheRationalUnifiedProcessisagenericprocessmodelthatseparatesactivitiesfromphases.

•CASEtechnologysupportssoftwareprocessactivities.

Waterfallmodel:

PPT3

WhatisSoftwareprojectmanagement?

Concernedwithactivitiesinvolvedinensuring

thatsoftwareisdeliveredontimeandon

scheduleandinaccordancewiththe

requirementsoftheorganisationsdeveloping

andprocuringthesoftware.

CriticalPath

•Longestofallpathsthroughtheproject

•Pathwithzerofloattime

◦Float（slack）>0meansthatextratimeisavailable.

◦Float（slack）=0meansthesituationiscritical.

◦Float（slack）<0meanstheprojectisbehindschedule,criticallylate.

•Minimumtimetocompletetheproject

WBS:

workbreakdownstructure

 A treestructure,whichshowsasubdivisionofeffortrequiredtoachieveanobjective,atoolusedtodefineandgroupa project'sdiscreteworkelements（or tasks）inawaythathelpsorganizeanddefinethetotalworkscopeoftheproject.

Milestonesvs.Deliverables

Milestones:

Recognizableendpointofasoftwareactivity.（Shouldmakesomeoutput:

document,donothavetobelarge）

Deliverables:

Aprojectresultthatisdeliveredtothecustomer.（Usuallyattheendofsomemajorprojectphase）

Deliverablesareusuallymilestone,butmilestonesdonothavetobedeliverables.

•Thereisnotasimplerelationshipbetweenthepricechargedforasystemanditsdevelopmentcosts.开发成本和收费价格不是一个简单的关系

•Factorsaffectingproductivityincludeindividualaptitude,domainexperience,thedevelopmentproject,theprojectsize,toolsupportandtheworkingenvironment.

影响生产里的因素包括个人态度，领域经验，开发项目，项目规模，工具支持和工作环境

•Softwaremaybepricedtogainacontractandthefunctionalityadjustedtotheprice.

可以就软件价格来制定一份合同，用来调整其的价格

•Differenttechniquesofcostestimationshouldbeusedwhenestimatingcosts.

估算成本时应根据不同的技术来估算其的成本

•TheCOCOMOmodeltakesproject,product,personnelandhardwareattributesintoaccountwhenpredictingeffortrequired.

COCOMO（建设性成本模型）在预测所需工作量时考虑了项目，产品，人员和硬件的属性

•Algorithmiccostmodelssupportquantitativeoptionanalysisastheyallowthecostsofdifferentoptionstobecompared.

成本建模算法支持定量分析，因为他们允许选择不同方案的成本进行比较

•Thetimetocompleteaprojectisnotproportionaltothenumberofpeopleworkingontheproject.

完成项目的时间不与项目工作的人数成正比

PPT4

WhatisSoftwareRequirement?

•Itmayrangefromahigh-levelabstractstatementofaserviceorofasystemconstrainttoadetailedmathematicalfunctionalspecification.

Whodoesit?

REengineer?

?

?

Whyisitimportant?

TheHighCostofRequirementErrorscouldevenleadtothefailureofthewholeproject（product）.

Whatarethesteps?

◦Feasibilitystudies

◦Requirementselicitation;

◦Requirementsanalysis;

◦Requirementsvalidation;

◦Requirementsmanagement.

Whatistheworkproduct（artifacts）?

HowdoIensurethatI’vedoneitright?

Usingrequirementvalidationtechnique,checkthe:

•Validity.Doesthesystemprovidethefunctionswhichbestsupportthecustomer’sneeds?

•Consistency.Arethereanyrequirementsconflicts?

•Completeness.Areallfunctionsrequiredbythecustomerincluded?

•Realism.Cantherequirementsbeimplementedgivenavailablebudgetandtechnology

•Verifiability.Cantherequirementsbechecked?

WhataretheCASEforourrequirementanalysis?

•Requirementsstorage

◦Requirementsshouldbemanagedinasecure,manageddatastore.

•Changemanagement

◦Theprocessofchangemanagementisaworkflowprocesswhosestagescanbedefinedandinformationflowbetweenthesestagespartiallyautomated.

变更管理的过程是在信息流之间部分自动化的可以被定义的工作流程的阶段

•Traceabilitymanagement

◦Automatedretrievalofthelinksbetweenrequirements.

Points:

•Userrequirements

◦Statementsinnaturallanguageplusdiagramsoftheservicesthesystemprovidesanditsoperationalconstraints.Writtenforcustomers.

•Systemrequirements

◦Astructureddocumentsettingoutdetaileddescriptionsofthesystem’sfunctions,servicesandoperationalconstraints.Defineswhatshouldbeimplementedsomaybepartofacontractbetweenclientandcontractor.

◦一个结构化文件，详细的列出了系统的功能与服务和运作上的限制，定义了客户和承包商之间的合同的一部分该怎样实施

•Functionalrequirements

◦Statementsofservicesthesystemshouldprovide,howthesystemshouldreacttoparticularinputsandhowthesystemshouldbehaveinparticularsituations.

•Non-functionalrequirements

◦Constraintsontheservicesorfunctionsofferedbythesystemsuchastimingconstraints,constraintsonthedevelopmentprocess,standards,etc.

Requirementsengineeringprocesses

•TheprocessesusedforREvarywidelydependingontheapplicationdomain,thepeopleinvolvedandtheorganisationdevelopingtherequirements.

•However,thereareanumberofgenericactivitiescommontoallprocesses

◦Requirementselicitation;

◦Requirementsanalysis;

◦Requirementsvalidation;

◦Requirementsmanagement.

需详细理解。

Feasibilitystudies

•Afeasibilitystudydecideswhetherornottheproposedsystemisworthwhile.

•Ashortfocusedstudythatchecks

◦Ifthesystemcontributestoorganisationalobjectives;

◦Ifthesystemcanbeengineeredusingcurrenttechnologyandwithinbudget;

◦Ifthesystemcanbeintegratedwithothersystemsthatareused.

Elicitationandanalysis

•Sometimescalledrequirementselicitationorrequirementsdiscovery.

•Involvestechnicalstaffworkingwithcustomerstofindoutabouttheapplicationdomain,theservicesthatthesystemshouldprovideandthesystem’soperationalconstraints.

•Mayinvolveend-users,managers,engineersinvolvedinmaintenance,domainexperts,tradeunions,etc.Thesearecalledstakeholders.

Requirementsvalidation

•Concernedwithdemonstratingthattherequirementsdefinethesystemthatthecustomerreallywants.

•Requirementserrorcostsarehighsovalidationisveryimportant

◦Fixingarequirementserrorafterdeliverymaycostupto100timesthecostoffixinganimplementationerror.

Requirementsmanagement

•Requirementsmanagementistheprocessofmanagingchangingrequirementsduringtherequirementsengineeringprocessandsystemdevelopment.

•Requirementsareinevitablyincompleteandinconsistent

◦Newrequirementsemergeduringtheprocessasbusinessneedschangeandabetterunderstandingofthesystemisdeveloped;

◦Differentviewpointshavedifferentrequirementsandtheseareoftencontradictory.

PPT5

●各种架构如：

Client-Server，data-centricetc.各自的优缺点；适应性等（如给定一个需求，给出架构设计设想）

●分布式体系架构

Points：

Softwarearchitecture

•Thedesignprocessforidentifyingthesub-system