网上图书购销系统的设计 外文翻译.docx

网上图书购销系统的设计 外文翻译.docx

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网上图书购销系统的设计外文翻译

毕业设计（论文）

外文翻译

题目网上图书购销系统的设计

专业信息管理与信息系统

班级09信管

（2）

学生张倩炜（20907234）

指导教师胡元义

高科学院

2013年

C#andDatabaseDevelopment

一、TheIntroduceofC#

Inonesense,C#canbeseenasbeingthesamethingtoprogramminglanguagesas.NETistotheWindowsenvironment.JustasMicrosofthasbeenaddingmoreandmorefeaturestoWindowsandtheWindowsAPIoverthepastdecade,VisualBasicandC++haveundergoneexpansion.AlthoughVisualBasicandC++haveendedupashugelypowerfullanguagesasaresultofthis,bothlanguagesalsosufferfromproblemsduetothelegaciesofhowtheyhaveevolved.

InthecaseofVisualBasic6andearlier,themainstrengthofthelanguagewasthefactthatitwassimpletounderstandanddidn’tmakemanyprogrammingtaskseasy,largelyhidingthedetailsoftheWindowsAPIandtheCOMcomponentinfrastructurefromthedeveloper.ThedownsidetothiswasthatVisualBasicwasnevertrulyobject-oriented,sothatlargeapplicationsquicklybecomedisorganizedandhardtomaintain.Aswellasthis,becauseVisualBasic’ssyntaxwasinheritedfromearlyversionsofBASIC（which,inturn,wasdesignedtobeintuitivelysimpleforbeginningprogrammerstounderstand,ratherthantowritelargecommercialapplications）,itdidn’treallylenditselftowell-structuredorobject-orientedprograms.

C++,ontheotherhand,hasitsrootsintheANSIC++languagedefinition.Itisn’tcompletelyANSIcompliantforthesimplereasonthatMicrosoftfirstwroteitsC++compilerbeforetheANSIdefinitionhadbecomeofficial,butitcomesclose.Unfortunately,thishasledtotwoproblems.First,ANSIC++hasitsrootsinadecade-oldstateoftechnology,andthisshowsupinalackofsupportformodernconcepts（suchasUnicodestringsandgeneratingXMLdocumentation）,andinsomearchaicsyntaxstructuresdesignedforthecompilersofyesteryear（suchastheseparationofdeclarationfromdefinitionofmemberfunctions）.Second,MicrosofthasbeensimultaneouslytryingtoevolveC++intoalanguagethatisdesignedforhigh-performancetasksonWindows,andinordertoachievethatthey’vebeenforcedtoaddahugenumberofMicrosoft-specifickeywordsaswellasvariouslibrariestothelanguage.

TheresultisthatonWindows,thelanguagehasbecomeacompletemess.JustaskC++developershowmanydefinitionsforastringtheycanthinkof:

char*,LPTSTR,string,CString（MFCversion）,CString（WTLversion）,wchar_t*,OLECHAR*,andsoon.

Nowenter.NET—acompletelynewenvironmentthatisgoingtoinvolvenewextensionstobothlanguages.MicrosofthasgottenaroundthisbyaddingyetmoreMicrosoft-specifickeywordstoC++,andbycompletelyrevampingVisualBasicintoVisualBasic.NET,alanguagethatretainssomeofthebasicVBsyntaxbutthatissodifferentindesignthatwecanconsiderittobe,forallpracticalpurposes,anewlanguage.

It’sinthiscontextthatMicrosofthasdecidedtogivedevelopersanalternative—alanguagedesignedspecificallyfor.NET,anddesignedwithacleanslate.VisualC#.NETistheresult.Officially,MicrosoftdescribesC#asa“simple,modern,object-oriented,andtype-safeprogramminglanguagederivedfromCandC++.”Mostindependentobserverswouldprobablychangethatto“derivedfromC,C++,andJava.”Suchdescriptionsaretechnicallyaccuratebutdolittletoconveythebeautyoreleganceofthelanguage.Syntactically,C#isverysimilartobothC++andJava,tosuchanextentthatmanykeywordsarethesame,andC#alsosharesthesameblockstructurewithbraces（{}）tomarkblocksofcode,andsemicolonstoseparatestatements.ThefirstimpressionofapieceofC#codeisthatitlooksquitelikeC++orJavacode.Behindthatinitialsimilarity,however,C#isaloteasiertolearnthanC++,andofcomparabledifficultytoJava.Itsdesignismoreintunewithmoderndevelopertoolsthanbothofthoseotherlanguages,andithasbeendesignedtogiveus,simultaneously,theeaseofuseofVisualBasic,andthehigh-performance,low-levelmemoryaccessofC++ifrequired.SomeofthefeaturesofC#are:

❑Fullsupportforclassesandobject-orientedprogramming,includingbothinterfaceandimplementationinheritance,virtualfunctions,andoperatoroverloading.

❑Aconsistentandwell-definedsetofbasictypes.

❑Built-insupportforautomaticgenerationofXMLdocumentation.

❑Automaticcleanupofdynamicallyallocatedmemory.

❑Thefacilitytomarkclassesormethodswithuser-definedattributes.Thiscanbeusefulfordocumentationandcanhavesomeeffectsoncompilation（forexample,markingmethodstobecompiledonlyindebugbuilds）.

❑Fullaccesstothe.NETbaseclasslibrary,aswellaseasyaccesstotheWindowsAPI（ifyoureallyneedit,whichwon’tbeallthatoften）.

❑Pointersanddirectmemoryaccessareavailableifrequired,butthelanguagehasbeendesignedinsuchawaythatyoucanworkwithouttheminalmostallcases.

❑SupportforpropertiesandeventsinthestyleofVisualBasic.

❑Justbychangingthecompileroptions,youcancompileeithertoanexecutableortoalibraryof.NETcomponentsthatcanbecalledupbyothercodeinthesamewayasActiveXcontrols（COMcomponents）.

❑C#canbeusedtowriteASP.NETdynamicWebpagesandXMLWebservices.

Mostoftheabovestatements,itshouldbepointedout,doalsoapplytoVisualBasic.NETandManagedC++.ThefactthatC#isdesignedfromthestarttoworkwith.NET,however,meansthatitssupportforthefeaturesof.NETisbothmorecomplete,andofferedwithinthecontextofamoresuitablesyntaxthanforthoseotherlanguages.WhiletheC#languageitselfisverysimilartoJava,therearesomeimprovements:

inparticular,Javaisnotdesignedtoworkwiththe.NETenvironment.

Beforeweleavethesubject,weshouldpointoutacoupleoflimitationsofC#.Theoneareathelanguageisnotdesignedforistime-criticalorextremelyhighperformancecode—thekindwhereyoureallyareworriedaboutwhetheralooptakes1,000or1,050machinecyclestorunthrough,andyouneedtocleanupyourresourcesthemillisecondtheyarenolongerneeded.C++islikelytocontinuetoreignsupremeamonglow-levellanguagesinthisarea.C#lackscertainkeyfacilitiesneededforextremelyhighperformanceapps,includingtheabilitytospecifyinlinefunctionsanddestructorsthatareguaranteedtorunatparticularpointsinthecode.However,theproportionsofapplicationsthatfallintothiscategoryareverylow.

二、databasedevelopmentprocess

Basedoninformationengineeringinformationsystemsplanningdatabaseisasourceofdevelopmentprojects.Thesenewdatabasedevelopmentprojectsisusuallyinordertomeetthestrategicneedsoforganizations,suchasimprovingcustomersupport,improveproductandinventorymanagement,oramoreaccuratesalesforecast.However,manymoredatabasedevelopmentprojectisthebottom-upapproachemerging,suchasinformationsystemuserneedsspecificinformationtocompletetheirwork,thusbeginningaprojectrequest,andasotherinformationsystemsexpertsfoundthatorganizationsneedtoimprovedatamanagementandbeginnewprojects.Bottom-upeveninthecircumstances,tosetupanenterprisedatamodelisalsonecessarytounderstandtheexistingdatabasecanprovidethenecessarydata,otherwise,thenewdatabase,dataentitiesandattributescanbeaddedtothecurrentdataresourcestotheorganization.

Boththestrategicneedsoroperationalinformationneedsofeachdatabasedevelopmentprojectsnormallyconcentratedinadatabase.Someprojectsonlyconcentratedinthedatabasedefinition,designandimplementationofadatabase,asafollow-uptothebasisofthedevelopmentofinformationsystems.However,inmostcases,thedatabaseandassociatedinformationprocessingfunctionasacompleteinformationsystemsdevelopmentprojectwaspartofthedevelopment.

1、SystemDevelopmentLifeCycle

Guidemanagementinformationsystemdevelopmentprojectsisthetraditionalprocessofsystemdevelopmentlifecycle（SDLC）.SystemdevelopmentlifecycleisanorganizationofthedatabasedesignersandprogrammersinformationsystemcomposedofthePanelofExpertsdetaileddescription,development,maintenanceandreplacementoftheentireinformationsystemsteps.ThisprocessisbecauseWaterfallthanforeverystepintotheadjacentthenextstep,thatis,theinformationsystemisaspecificationdevelopedbyapieceofland,everypieceoftheoutputisunderaninput.Howevershowninthefigure,thesestepsarenotpurelylinear,eachofthestepsoverlapintime（andthuscanmanageparallelsteps）,butwhentheneedtoreconsiderpreviousdecisions,butalsotorollbacksomestepsahead.（Andthereforewatercanbeputbackinthewaterfall!

）

Figure4onthesystemdevelopmentlifecycleandthepurposeofeachstageoftheproductcanbedeliveredconcisenotes.Thesystemdevelopmentlifecycleincludingeachstageanddatabasedevelopment-relatedactivities,therefore,thequestionofdatabasemanagementsystemsthroughouttheentiredevelopmentprocess.InFigure5werepeatofthesystemdevelopmentlifecyclestageoftheseven,andoutlinesthecommondatabaseateachstageofdevelopmentactivities.Pleasenotethatthesystemsdevelopmentlifecyclestagesanddatabasedevelopmentsteps一一existsbetweentherelationshipbetweentheconceptofmodelingdatainbothsystemsdevelopmentlifecyclestagesbetween.

EnterpriseModeling

Databasedevelopmentprocessfromtheenterprisemodeling（systemdevelopmentlifecyclestageoftheprojectfeasibilitystudies,andtochooseapart）,Organizationssetthescopeandgeneraldatabasecontent.Enterprisemodelingininformationsystemsplanningandother