软件工程毕业论文外文文献—软件工程.docx
- 文档编号:13642846
- 上传时间:2023-06-16
- 格式:DOCX
- 页数:27
- 大小:33.05KB
软件工程毕业论文外文文献—软件工程.docx
《软件工程毕业论文外文文献—软件工程.docx》由会员分享,可在线阅读,更多相关《软件工程毕业论文外文文献—软件工程.docx(27页珍藏版)》请在冰点文库上搜索。
外文原文
1、SoftwareEngineering
Softwareisthesequencesofinstructionsinoneormoreprogramminglanguagesthatcompriseacomputerapplicationtoautomatesomebusinessfunction.Engineeringistheuseoftoolsandtechniquesinproblemsolving.Puttingthetwowordstogether,softwareengineeringisthesystemticapplicationoftoolsandtechniquesinthedevelopmentofcomputer-basedapplications.
Thesoftwareengineeringprocessdescribesthestepsittakestodeelopthesystem.Webeginadevelopmentprojectwiththenotionthatthereisaproblemtobesolvedviaautomation.Theprocessishowyougetfromproblemrecognitiontoaworkingsolution.Aqualityprocessisdesirablebecauseitismorelikelytoleadtoaqualityproduct.Theprocessfollowedbyaprojectteamduringthedevelopmentlifecycleofanapplicationshouldbeorderly,goal-oriented,enjoyable,andalearningexperience.
Object-orientedmethodologyisanapproachtosystemlifecycledevelopmentthattakesatop-downviewofdataobjects,theirallowableactions,andtheunderlyingcommunicationrequirementtodefineasystemarchitecture.Thedataandactioncomponentsareencapsulated,thatis,theyarecombinedtogether,toformabstractdatatypesEncapsulationmeansthatifIknowwhatdataIwant,Ialsoknowtheallowableprocessesagainstthatdata.Dataaredesignedaslatticehierarchiesofrelationshipstoensurethattop-down,hierarchicinheritanceandsidewaysrelationshipsareaccommodated.Encapsulatedobjectsareconstrainedonlytocommunicateviamessages.Ataminimum,messagesindicatethereceiverandactionrequested.Messagesmaybemoreelaborate,includingthesenderanddatatobeactedupon.
Thatwetrytoapplyengineeringdisciplinetosoftwaredevelopmentdoesnotmeanthatwehavealltheanswersabouthowtobuildapplications.Onthecontrary,westillbuildsystemsthatarenotusefulandthusarenotused.Partofthereasonforcontinuingproblemsinapplicationdevelopment,isthatweareconstantlytryingtohitamovingtarget.Boththetechnologyandthetypeofapplicationsneededbybusinessesareconstantlychangingandbecomingmorecomplex.Ourabilitytodevelopanddisseminateknowledgeabouthowtosuccessfullybuildsystemsfornewtechnologiesandnewapplicationtypesseriouslylagsbehindtechnologicalandbusinesschanges.
Anotherreasonforcontinuingproblemsinapplicationdevelopmentisthatwearen’talwaysfreetodowhatwelikeanditishardtochangehabitsandculturesfromtheoldwayofdoingthings,aswellasgetuserstoagreewithanewsequenceofeventsoranunfamiliarformatfordocumentation.
Youmightaskthen,ifmanyorganizationsdon’tusegoodsoftwareengineeringpractices,whyshouldIbotherlearningthem?
Therearetwogoodanswerstothisquestion.First,ifyouneverknowtherightthingtodo,youhavenochanceofeverusingit.Second,organizationswillfrequentlyacceptevolutionary,smallstepsofchangeinsteadofrevolutionary,massivechange.Youcanlearnindividualtechniquesthatcanbeappliedwithoutcompletedevotiontoonewayofdevelopingsystems.Inthisway,softwareengineeringcanspeedchangeeintheirorganizationsbydemonstratinghowthetoolsandtechniquesenhancethqualityofboththeproductandtheprocessofbuildingasystem.
2、DataBaseSystem
1、Introduction
Thedevelopmentofcorporatedatabaseswillbeoneofthemostimportantdata-processingactivitiesfortherestofthe1970s.Datewillbeincreasinglyregardedasavitalcorporateresource,whichmustbeorganizedsoastomaximizetheirvalue.Inadditiontothedatabaseswithinanorganization,avastnewdemandisgrowingfordatabaseservices,whichwillcollect,organize,andselldata.
Thefilesofdatawhichcomputerscanusearegrowingatastaggeringrate.Thegrowthrateinthesizeofcomputerstorageisgreaterthanthegrowthinthesizeorpowerofanyothercomponentintheexplodingdataprocessingindustry.Themoredatathecomputershaveaccessto,thegreateristheirpotentialpower.Inallwalksoflifeandinallareasofindustry,databankswillchangetheareasofwhatitispossibleformantodo.Intheendofthiscentury,historianswilllookbacktothecomingofcomputerdatabanksandtheirassociatedfacilitiesasastepwhichchangedthenatureoftheevolutionofsociety,perhapseventuallyhavingagreatereffectonthehumanconditionthaneventheinventionoftheprintingpress.
Somemostimpressivecorporategrowthstoriesofthegenerationarelargelyattributabletotheexplosivegrowthintheneedofinformation.
Thevastmajorityofthisinformationisnotyetcomputerized.However,thecostofdatastoragehardwareisdroppingmorerapidlythanothercostsindataprocessing.Itwillbecomecheapertostoredataoncomputerfilesthantostorethemonpaper.Notonlyprintedinformationwillbestored.Thecomputerindustryisimprovingitscapabilitytostorelinedrawing,datainfacsimileform,photo-graphs,humanspeech,etc.Infact,anyformofinformationotherthanthemostintimatecommunicationsbetweenhumanscanbetransmittedandstoreddigitally.
Therearetwomaintechnologydevelopmentslikelytobecomeavailableinthenearfuture.First,thereareelectromagneticdevicesthatwillholdmuchmoredatathandisksbuthavemuchlongeraccesstime.Second,therearesolid-statetechnologiesthatwillgivemicrosecondaccesstimebutcapacitiesaresmallerthandisks.
Disksthemselvesmaybeincreasedincapacitysomewhat.Forthelongertermfuturethereareanumberofnewtechnologieswhicharecurrentlyworkinginresearchlabswhichmayreplacedisksandmayprovideverylargemicrosecond-access-timedevices.Asteadystreamofnewstoragedevicesisthuslikelytoreachthemarketplaceoverthenext5years,rapidlyloweringthecostofstoringdata.
Giventheavailabletechnologies,itislikelythaton-linedatabaseswillusetwoorthreelevelsofstorage.Onesolid-statewithmicrosecondaccesstime,oneelectromagneticwithaccesstimeofafractionofasecond.Iftwo,three,orfourlevelsofstorageareused,physicalstorageorganizationwillbecomemorecomplex,probablywithpagingmechanismstomovedatabetweenthelevels;solid-statestorageoffersthepossibilityofparallelsearchoperationandassociativememory.
Boththequantityofdatastoredandthecomplexityoftheirorganizationaregoingupbyleapsandbounds.Thefirsttrillionbiton-linestoresarenowinuse.inafewyear’stime,storesofthissizemaybecommon.
Aparticularlyimportantconsiderationindatabasedesignistostorethedatasothatthecanbeusedforawidevarietyofapplicationsandsothatthewaytheycanbechangedquicklyandeasily.Oncomputerinstallationpriortothedatabaseeraithasbeenremarkablydifficulttochangethewaydataareused.Differentprogrammersviewthedataindifferentwaysandconstantlywanttomodifythemasnewneedsarisemodification,however,cansetoffachainreactionofchangestoexistingprogramsandhencecanbeexceedinglyexpensivetoaccomplish.
Consequently,dataprocessinghastendedtobecomefrozenintoitsolddatastructures.
Toachieveflexibilityofdatausagethatisessentialinmostcommercialsituations.Twoaspectsofdatabasedesignareimportant.First,itshouldbepossibletointerrogateandsearchthedatabasewithoutthelengthyoperationofwritingprogramsinconventionalprogramminglanguages.Second,thedatashouldbeindependentoftheprogramswhichusethemsothattheycanbeaddedtoorrestructuredwithouttheprogramsbeingchanged.
Theworkofdesigningadatabaseisbecomingincreasingdifficult,especiallyifitistoperforminanoptimalfashion.Therearemanydifferentwaysinwhichdatacanbestructured,andtheyhavedifferenttypesofdataneedtobeorganizedindifferentways.Differentdatahavedifferentcharacteristics,whichoughttoeffectthedataorganization,anddifferentusershavefundamentallydifferentrequirements.Soweneedakindofdatabasemanagementsystem(DBMS)tomanagedata.
Databasedesignusingtheentity-relationshipmodelbeginswithalistoftheentitytypesinvolvedandtherelationshipsamongthem.Thephilosophyofassumingthatthedesignerknowswhattheentitytypesareattheoutsetissignificantlydifferentfromthephilosophybehindthenormalization-basedapproach.
Theentity-relationship(E-R)approachusesentity-relationshipdiagrams.TheE-RapproachrequiresseveralstepstoprodureastructurethatisacceptablebytheparticularDBMS.Thesestepsare:
(1) Dataanalysis
(2) Producingandoptimizingtheentitymodel.
(3) Logicalschemadevelopment
(4) Physicaldatabasedesignprocess.
Developingadatabasestructurefromuserrequirementsiscalleddatabasesdesign.Mostpractitionersagreethattherearetwoseparatephasestothedatabasedesignprocess.Thedesignofalogicaldatabasestructurethatisprocessablebythedatabasemanagementsystem(DBMS)describestheuser’sviewofdata,andistheselectionofaphysicalstructuresuchastheindexedsequentialordirectaccessmethodoftheintendedDBMS.
Currentdatabasedesigntechnologyshowsmanyresidualeffectsofitsoutgrowthfromsingle-recordfiledesignmethods.Filedesignisprimarilyapplicationprogramdependentsincethedatahasbeendefinedandstructuredintermsofindividualapplicationstousethem.TheadventofDBMSrevisedtheemphasisindataandprogramdesignapproaches.
Therearemanyinterlockingquestionsinthedesignofdata-basesystemsandmanytypesoftechniquethatonecanuseisanswertothequestionsomany;infact,thatoneoftenseesvaluableapproachesbeingoverlookedinthedesignandvitalquestio
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 软件工程 毕业论文 外文 文献