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People（mostimportant）
Tools
Method
Process
●WhatisthedifferencebetweenSE（softwareengineering）andCS（computerscience）?
Computerscienceisconcernedwiththeoryandfundamentals;
softwareengineeringisconcernedwiththepracticalitiesofdevelopinganddelivering（交付）usefulsoftware.
●Whatisthedifferencebetweensoftwareengineeringandsystemengineering?
systemengineeringisconcernedwithallaspectsofcomputer-basedsystemsdevelopment,includinghardwaresoftwareandprocessengineering（处理工程）.softwareengineeringisapartofthisprocess.
●Whatissoftwareprocess?
Asetofactivitieswhosegoalisthedevelopmentorevolutionofsoftware.
Genericactivitiesinallsoftwareprocessesare:
Specification（描述）-whatthesystemshoulddoanditsdevelopmentconstraints
Development（开发）-productionofthesoftwaresystem
Validation（有效性验证）-checkingthatthesoftwareiswhatthecustomerwants
Evolution（进化）-changingthesoftwareinresponsetochangingdemands.
●Whatissoftwareprocessmodel?
Asimplifiedrepresentation（表示形式）ofasoftwareprocess,presentedfromaspecificperspective.
softwareprocessmodel：
Workflowperspective-sequenceofactivities;
Data-flowperspective-informationflow;
Role/actionperspective-whodoeswhat.
软件过程部分
●Genericprocessmodels
Ø
Waterfall;
（瀑布型）
——Separateanddistinctphasesofspecificationanddevelopment.（使用单独的过程阶段表现）
问题：
1.Inflexible（Onephasehastobecompletebeforemovingontothenextphase.）
2.Transferofrisks（风险转移）
适用：
mostlyusedforlargesystemsengineeringprojectswhereasystemisdevelopedatseveralsites
Evolutionarydevelopment;
（进化式）
——Specification,developmentandvalidationareinterleaved（交替，先快速开发再不断修改）.
Exploratorydevelopment（探索式）：
toworkwithcustomers
Throw-awayprototyping（抛弃式）：
startwithpoorlyunderstoodrequirementstoclarifywhatisreallyneeded
1Lackofprocessvisibility（过程不可见）
2Systemsareoftenpoorlystructured
Forsmallormedium-sizeinteractivesystems
Component-basedsoftwareengineering.（基于组件CBSE）
——Thesystemisassembledfromexistingcomponents.（集成已存在的可复用的组件）
软件复用reuse：
peopleworkingontheprojectknowofdesignsorcodewhichissimilartothatrequired.
●Processiteration软件迭代：
（Iterationcanbeappliedtoanyofthegenericprocessmodels.）
两个过程模型专门为过程反复设计的
Two（related）approaches：
Incrementaldelivery（增量式开发）;
——thedevelopmentanddeliveryisbrokendownintoincrements（增量）
Thehighestpriorityrequirementsareincludedinearlyincrements
Oncethedevelopmentofanincrementisfinished，correspondingsystemfunctionalityisavailable
Spiraldevelopment（螺旋式开发）.
——Eachloop（循环）inthespiralrepresentsaphaseintheprocess.
Risksareexplicitlyassessedandresolvedthroughouttheprocess.
●Fourfundamentalprocessactivities:
•Softwarespecification
•Softwaredesignandimplementation
•Softwarevalidation
•Softwareevolution
Softwarespecification（描述）
Softwaredesignandimplementation（设计和实现）
Softwarevalidation（有效性验证）
Verificationandvalidation（V&
V）V&
Vmustbeappliedateachstageinthesoftwareprocess.
Hastwoprincipalobjectives：
Thediscoveryofdefectsinasystem;
Theassessmentofwhetherornotthesystemisusefulanduseableinanoperationalsituation
Verification:
"
Arewebuildingtheproductright”.——Thesoftwareshouldconformtoitsspecification.
Validation:
Arewebuildingtherightproduct”.——Thesoftwareshoulddowhattheuserreallyrequires.
Softwareevolution（进化）
软件项目管理部分
●Softwareprojectmanagement
Concernedwithactivitiesinvolvedinensuringthatsoftwareisdeliveredontimeandonscheduleandinaccordancewiththerequirementsoftheorganisationsdevelopingandprocuringthesoftware.
●MilestonesVs.Deliverables
Milestonesaretheend-pointofaprocessactivity.（里程碑）
Deliverablesareprojectresultsdeliveredtocustomers.（可交付的文档）
软件过程被分解为一系列想关的基本活动，每个基本活动都有相应的输出结果。
里程碑不是要交给客户的东西。
而可交付的文档是要交付给客户的项目成果，要在项目的描述、设计等阶段结束时交付。
例如需求过程：
可交付的文档是：
需求描述
●CriticalPath
Longestofallpathsthroughtheproject
●WBS
软件需求部分
●SoftwareRequirementVs.SoftwareRequirementEngineering
Requirement：
Itmayrangefromahigh-levelabstractstatementofaserviceorofasystemconstrainttoadetailedmathematicalfunctionalspecification.Descriptionofsystemservicesandconstraintstoadetailmathematicalfunction.
Requirementsengineering：
Theprocessofestablishingtheservicesthatthecustomerrequiresfromasystemandtheconstraintsunderwhichitoperatesandisdeveloped.
Therequirementsthemselvesarethedescriptionsofthesystemservicesandconstraintsthataregeneratedduringtherequirementsengineeringprocess.
●软件需求类型
用户需求（userrequirement）
Statementsinnaturallanguageplusdiagramsoftheservicesthesystemprovidesanditsoperationalconstraints.Writtenforcustomers.
系统需求（systemrequirement）
Astructureddocumentsettingoutdetaileddescriptionsofthesystem’sfunctions,servicesandoperationalconstraints.Defineswhatshouldbeimplementedsomaybepartofacontractbetweenclientandcontractor.
系统需求包括：
功能性需求（Functionalrequirements）
Statementsofservicesthesystemshouldprovide,howthesystemshouldreacttoparticularinputsandhowthesystemshouldbehaveinparticularsituations.
Functionaluserrequirementsmaybehigh-levelstatementsofwhatthesystemshoulddo
Functionalsystemrequirementsshoulddescribethesystemservicesindetail.
非功能性需求（non-functionalrequirements）
constraintsontheservicesorfunctionsofferedbythesystemsuchastimingconstraints,constraintsonthedevelopmentprocess,standards,etc.
需求工程过程（从可行性分析到需求文档，这部分包括很多细致的内容，请参考教材和ppt）
Requirementsengineeringprocess：
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.
ReviewQuestionsforyou!
●WhatisSoftwareRequirement?
●Whodoesit?
●Whyisitimportant?
●Whatarethesteps?
●Whatistheworkproducts（artifacts）?
●HowdoIensurethatI’vedoneitright?
●WhataretheCASEforourrequirementanalysis?
软件体系架构设计部分
●SoftwareArchitectureVs.ArchitectureStyle
Thedesignprocessforidentifyingthesub-systemsmakingupasystemandtheframeworkforsub-systemcontrolandcommunicationisarchitecturaldesign.
Theoutputofthisdesignprocessisadescriptionofthesoftwarearchitecture.
软件设计部分
SoftwareDesign:
Designiswhatvirtuallyeveryengineerwantstodo.Itistheplacewherecreativelyrules-customersrequirements,businessneeds,andtechnicalconsiderationsallcometogetherintheformulationofaproductorsystem.
DesignPrinciples:
•Abstraction抽象
抽象是控制复杂性的基本策略。
“抽象”要求人们将注意力集中在某一层次上考虑问题，而忽略那些低层次的细节。
•Modularity模块性
•InformationHiding信息隐藏
•FunctionalIndependence功能独立
Coupling耦合——单元模块之间
Onemoduleisreferencedbyothermodules
Datatransportedfromonemoduletotheothers
耦合度是对软件结构中模块间关联程度的一种度量。
耦合的强弱取决于模块间接口的复杂性、进入或调用模块的位置以及通过界面传送数据的多少等。
与内聚度正好相反，在设计软件时应追求尽可能松散耦合的系统。
因为对这类系统中任一模块的设计、测试和维护相对独立。
由于模块间联系较少，错误在模块间传播的可能性也随之变小。
模块间的耦合程度直接影响系统的可理解性、可测试性、可靠性和可维护性。
耦合度也可以分为七级
Lowercoupling
No-directCoupling
无联系耦合：
如果两模块中任一个都不依赖于对方能独立工作，则称这两模块为（nodirectcoupling），这类耦合度最低。
DataCoupling
StampCoupling:
特征耦合：
介于数据耦合和控制耦合之间的一种耦合
印记耦合：
将数据结构作为参数进行传递
ControlCoupling:
控制耦合：
传递标志
如果两模块间通过参数交换信息，此时若传递的信息中含有控制信息，则耦合度上升为控制耦合。
控制耦合通常会增加系统的复杂性，有时适当分解模块可消除控制耦合。
Externalcoupling
外部耦合：
一些模块都与一个外部环境相关，
升级会员 