letsaspweb服务器

MassachusettsInstituteofTechnologyDepartmentofUrbanStudiesandPlanning11.
520:AWorkshoponGeographicInformationSystems11.
188:UrbanPlanningandSocialScienceLaboratoryLecture10:IntroductiontoInternetGISandArcIMSNov.
9,2005,JosephFerreira,Jr.
BasedprimarilyonlecturenotesbyVisitingProf.
Zhong-RenPeng,Fall,2003See:PengandTsou,InternetGIS,2003,JohnWiley,ISBN:0-471-35923-8.
MainTopic:IntroductiontoInternetGISandArcIMSIntroductiontoInternetGISStateoftheArtofInternetGISIntroductiontoArcIMSTheRoadMapofGISStand-aloneGISProgramsMainframe-basedmonolithicGISprogramsDesktopGISprogramsLimitedornocommunicationwithothercomputers(otherthantransparentlyvia,forexample,useofanetworkfileserver)ProgramsneedtorunonthemainframeorPCwheretheprogramresidesUsersneedaccesstothatmachineviaaloginordumbterminalsession.
Examples:earlyArc/Infoinstalledonastand-alonemainframeorPC.
LAN-basedGISProgramsGISinstalledononeormoremachinesonaLocalAreaNetwork(LAN)GISprogramsrunonlocalmachinesbutcansharedataandprintingfacilitiesfromthedataserver,orGISprogramsrunonaserver,usercanaccessitfromanymachineinsidetheLAN.
TypicalClient/Serverarchitecture.
Examples:MostcurrentGISprograms.
LimitationsofStand-AloneandLAN-basedGISProgramsDifficultforuseroutsidetheLANtoaccess.
DifficulttodirectlyaccessdatathatareavailableoutsidetheLAN.
LimitedGISusers.
Difficulttomange,updateandextend.
WhatisInternetGISInternetGISisanetwork-centricGIStoolthatusestheInternetasaprimarymeansofprovidingaccesstothefunctionality(e.
g.
,analysistools,mappingcapability)ofGISandtothespatialdataandotherdataneededforvariousGISapplications.
InternetGISisanintegratedclient/server,andWeb/Serverapplication.
InternetGIStypicallyusesaWebbrowserasclient.
InternetGIScanbeviewedasadistributed,object-orientedsystem.
InternetGISisportableandcross-platform.
InternetGISvsWebGISWhat'sthedifferencebetweentheInternetandtheWorldWideWebInternetreferstotheinter-connectedcomputernetwork,--infrastructure.
WebisoneofmanyapplicationsthatarebasedontheInternet.
ThetermInternetGISfocusestheuseofasuiteofInternettechnologies,notonlytheWeb.
InternetGISthushasmorelongevityandisapreferredterm.
FeaturesofInternetGISWideaccessibility,usersfromtheworldcanaccessGISdataandanalysistoolsovertheInternet.
NoGISsoftwareisrequiredtoinstalllocally.
TakesadvantageofthefriendlygraphicuserinterfacethatisprovidedbytheWorldWideWeb.
UserscandirectlymanipulatemapsandGISdataovertheWeb.
Internet-awareGISsoftwarecanaccessremotedataanywhereontheInternet.
InternetGIScaneasilyincorporateup-to-date,real-timeinformationBasicComponentsoftheInternetGISInternetGIS:StateoftheArtStaticMappublishingStaticWebMappingInteractiveWebMappingClient-sidePlug-insandHelperProgramGISActiveXControlsJava-basedInternetGISDistributedGeographicInformationServicesServer-SideandClient-SideInternetGISServer-SideInternetGISHTMLtoGISserverviaCGI(CommonGatewayInterface)scriptClient-SideInternetGISClient-sidePlug-insandHelperProgramGISActiveXControlsJava-basedInternetGISHybridofserver-andclient-sideInternetGISStaticMappublishingInsertMapimagesinatextfileontheWeb.
NotaGIS.
StaticWebMappingHowdoesitworkCommonGatewayInterfaceWheninformationiscollectedbyabrowseritissenttoaHyperTextTransferProtocol(HTTP)serverspecifiedintheHTMLform,andthatserverstartsaprogram,alsospecifiedintheHTMLform,thatcanprocessthecollectedinformation.
Suchprogramsareknownas"CommonGatewayInterface"programs,orCGIscripts(E.
O.
Johnson).
CGIisasimpleinterfacethatlinksWebbrowser,serverandotherexternalprograms.
CGIorDynamicLinkLibrary(DLL)hasthreefunctions:ItreceivesuserinputsandparsesthemintoparametersofvariablestobeusedinGISprograms.
ItletsWebserversrunotherGISprograms.
Itinterpretsoutputandsendsbacktobrowsers.
AdvantagesofStaticWebMappingA"thin"client(e.
g.
,alldataprocessingisdoneontheserver,whiletheclientisusedonlyfordisplayanduserinput).
TakesfulladvantageofallGISsoftwarefunctionalityattheserver.
UbiquitouslyaccessibleovertheInternet.
CanhandlelargedatabasetoservespatialqueriesDrawbacksofStaticWebMappingEveryuserrequesthastogothroughtheInternettoactivateaCGIscripteverytime.
CreatesheavytrafficovertheInternet.
Operationisslow,becauseeverycommand(evenverysimpleoneslikezoomandpan)hastobeoperatedontheGISserver.
Mapsarestaticimages.
Usercannotdrawaboxoracircleorselectpolygonsonthemapimages.
ExamplesofStaticWebMappingVISAInternationalATMlocator(http://www.
visa.
com/)ESRI'sMapObjectsInternetMapServer(http://metro-trip.
ci.
waukesha.
wi.
us/waukesha/)MapQuest(http://www.
mapquest.
com/)InteractiveWebMapping(Client-SideInternetGIS)InteractiveWebMappingprogramsallowtheusertomanipulateGISdataandconductGISanalysisattheclient/userside,including:GISPlug-InsandHelperProgramsGISJavaAppletsGISActiveXControlsGISPlug-InsorHelperProgramsGISplug-insaresoftwareexecutablesthatrunonthebrowserandinterprettheGISdatareceivedfromtheserver.
GISplug-insareusedinextendingthebrowsertoprocessGISdata.
WhileGISplug-insaresmallapplications,GIShelperprogramscanbelargeGISapplicationsorexistingGISsoftwarethatislocatedintheuser'slocalmachine.
HowDoGISPlug-InsWorkPartitionPointsforGISPlug-InExamplesofGISPlug-insAutodesk:MapGuide(http://www.
mapguide.
com/)GeoMediaWebMap(forNetscapebrowser)AdvantagesofGISPlug-InsGISplug-insenableWebbrowsertointeractwithGISdata.
SomeGISfunctions(i.
e.
,zoom,pan,query)canbeconductedbytheplug-ins,soitcanreducetrafficontheInternet.
GISplug-inscanfetchdatafromtheserverondemand.
Plug-insareeasytocontrolandarenotdistributedwithbrowsers.
DrawbacksofGISPlug-InsPlug-insarenotplatform-independent.
TheGISvendorhastocreatedifferentplug-insfordifferentoperatingsystems(Unix,PC).
Usershavetodownloaddifferentplug-insfromdifferentGISservers.
GISplug-insandhelperprogramshavetobeinstalledintheuser'smachine.
Securityconcernsmakeusershesitanttodownloadplug-ins.
GISAppletsGISappletsareexecutablecodethataredownloadedfromtheserverandexecutedonthebrowserclientatruntime.
Javaappletsuseanobject-orientedlanguagedesignedtoworkonavirtualmachineandincludingfunctionalitythatisusefulfortheinterfacedesignofGISmappingandanalysisfunctions.
Javaappletsareinterpretedlocallyviatoolsthatareembeddedinthemostcommonbrowsers.
Java-BasedInternetGISHowdoesitworkExamplesofJava-BasedInternetGISMapXtremefromMapInfo(http://www.
mapinfo.
com/)Googlemaps(http://maps.
google.
com/)(usingAJAX:asynchronousjavascripttechnologyandXML:http://java.
sun.
com/developer/technicalArticles/J2EE/AJAX)ArcIMSfromESRI.
PartitionPointforGISAppletsTheappletmodelmovesthepartitioningpointfurthertotheright.
Appletgivestheapplicationdesigner/developertheflexibilitytodeterminewheretosplittheapplication.
Forexample,aWebservermaysupplydifferentappletsdependingonthespeedoftheconnectionbetweenitanditsclients.
AdvantagesofJava-basedInternetGISJava'sbytecodeisplatform-neutral,soitcanruninanymachinewithoutmodification.
Forvendorsanddevelopers,itmeanslargerpotentialmarketandtheeliminationof"softwareporting.
"Forusers,itmeanslowercostandgreaterinteroperabilityamongcomponents.
Javaappletisrunonlocalmachine,minimizingthrough-nettraffic,andmakingbetteruseoflocalcomputingresources.
Javaappletsaremoreflexibleincreatinganddisplayinggraphicsandmaps.
Javaappletsaredownloadedfromtheserveratruntimeandwilldisappearwhentheuserquitstheapplication.
Javaismoresecure,becauseappletsrunontheJVMontheuser'slocaldevice.
Javaappletshavenoaccesstolocalsystem.
DrawbacksofJavaAppletIttakessometimetoinitiallydownloadapplets.
Thisisespeciallyproblematicforslowconnections(e.
g.
,viadialupmodems).
ItneedsJava-enabledWebbrowserforJavaappletstofunction.
Itcannotaccesslocalfilesanddata(duetosecuritylimitationsofJavatools).
JavabasedWebGIScannotselectobjectsbyradiusorselectobjectfrommultiplethemes(E.
O.
Johnson).
JavaPlug-InOldJavaappletreliesonthewebbrowser'sdefaultvirtualmachine.
JavaPlug-insoftwareenablesenterprisecustomerstodirectappletsorJavaBeansontheirintranetwebpagestorunusingSun'sJava2RuntimeEnvironment,StandardEdition(JRE).
TheJavaplug-inallowsredistributionofbothstandaloneJavatechnology-basedapplicationsandbrowser-basedapplets(http://java.
sun.
com/products/plugin/).
GISActiveXControlsAnActiveXcontrolisapieceofexecutablecodethatcanrunonWindowsplatforms.
ActiveXcontrolsconformtotheCOM(ComponentObjectModel)standard.
Theyareloadedandexecutedinsideacontainer(InternetExplorer).
HowDoGISActiveXControlsWorkPartitionPointforActiveXControlsSameasforJavaAppletExampleofGISActiveXControlsIntergraph'sGeoMediaWebMapServer(http://imgs.
intergraph.
com/gmwm/)MapGuide(www.
mapguide.
com)AdvantagesofGISActiveXControlsOffersbetterperformance,becausetheyarecompiledtothenativeexecutableformat.
Takesfulladvantageoflocalmachineresourcesandplatformfunctionality(e.
g.
files,memory,hardwareandsoftwaresystemcontrols)unavailabletoaJavaapplet.
Canaccesstolocaldata.
AdvantagesofGISControlsSomeGISfunctions(i.
e.
,zoom,pan,query)canbeconductedbytheGIScontrols.
GIScontrolscanfetchdatafromtheserverondemand.
GIScontrolscancommunicatewithotherActiveXcontrolsanddatalocallyaswellasremotelyaslongastheyconformtotheCOMstandard.
DrawbacksofGISActiveXControlsPortability:platformdependent,differentActiveXcontrolsneedtobecreatedfordifferentplatforms.
UsershavetodownloaddifferentGIScontrolsfromdifferentGISvendors,suchasGIScontrolsfromESRI,Intergraph,etc.
NotallbrowserssupportActiveXcontrols.
Forexample,Netscapeneedsaplug-intorunActiveXcontrols.
GIScontrolshavetobeinstalledintheuser'smachineandleadtoa"fat"client.
Safety:BecauseActiveXcontrolshavefullaccesstoplatformservices,theycandogreatdamagetoalocalsystem.
Safetysolution:Useverificationapproachtoverifyifacontrolissuppliedbyatrustedsource.
Theassumptionisthatifitissuppliedbyatrustedsource,itshouldbesafetouse.
SafetyConcernsofActiveXControlsProblemswiththeverificationapproachTobesafe,userswouldhavetorejectallActiveXcontrolsnotsignedbyanauthority.
EveniftheusercanverifytheActiveXcontrolcomesfromareliablesource,thereisstillnowaytotellifexecutingthecontrolwillcausedamage.
DataStreamingontheInternetStreamingsubsetofdatatotheclient.
Fulldatasetstoredinthedataserver.
Theclienthasthecapabilitytoreplicateandcachedataontheclientside.
Thepresentation(displayandvisualization)andlogiccomponents(maprendering)oftheapplicationresideontheclientsideinordertointelligentlydisplaythedata.
Example:GoogleEarth'sclient:(http://earth.
google.
com)PartitionPointforDataStreamingAdvantagesofInteractiveWebMappingInteractiveWebmappingenablesWebbrowsertointeractwithvectordataratherthanstaticmapimages.
SomeGISfunctions(i.
e.
,zoom,pan,query)canbeconductedbytheclient-sideprograms,soitcanreducetrafficontheInternet.
Client-Sideprogramscanfetchdatafromtheserveratruntime.
DrawbacksofInteractiveWebmappingIttakessometimetoinitiallydownloadclient-sideInternetGISprograms.
Someclient-sideInternetGISprogramsarenotplatform-independent.
LimitedfunctionalityDifficulttohandleverylargedatabase,sincethetransportoflargeamountsofdataovertheInternetisslow.
IntroductiontoArcIMSArcIMSArchitectureArcIMSComponentsArcIMSClientViewersHTML/DHTMLViewerwrittenusingHTML,DHTML(dynamicHTML),andJavaScript.
AthinclientthatonlysupportsmapimagesontheWebbrowser.
Onlyoneimagecanbedisplayedatatime.
ColdFusionandActiveXViewersSimilartoHTML/DHTMLViewer,butthinnerJavaViewersupportbothImageandFeaturestreamingArcIMSBusinessLogicTierArcIMSWebServerReceivesrequestfromWebClient.
CommunicateswiththeWebclient(browser)throughHTTP.
ForwardsclientrequesttoApplicationServerviaApplicationServerConnector.
CommunicateswithApplicationServerthrougheitheraJavaServlet,orColdFusionortheActiveServerPages(ASP).
ApplicationServerConnectorTheconnectorsprovideacommunicationchannelbetweenaWebServerorathirdpartyapplicationserverandtheApplicationServer.
TheconnectorsestablishasocketconnectionwiththeApplicationServerforeachrequest.
Oncethecommunicationchannelisestablished,requestsaresenttoandresponsesarereceivedfromtheApplicationServer.
ArcIMSApplicationServerManagesloadandassignstaskstospatialservers.
ServesasabookkeeperforkeepingtrackofwhichMapServicesarerunningonwhichArcIMSSpatialServers.
AllocatesanincomingrequesttotheappropriateSpatialServer.
TheApplicationServercancommunicatewithMultipleWebServers.
ArcIMSSpatialServerThisisthebackboneofArcIMS.
Itcanproducemaps,accessdata,andbundlemapsintoanappropriateformatbasedontheuserrequests.
Itcontainsseveralsupportingcomponents:Weblink,theXMLparser,andtheDataAccessManager.
WeblinkisthecommunicationgatewaybetweentheArcIMSApplicationServerandtheSpatialServer.
TheXMLparserisusedforparsingArcXMLrequests.
TheDataAccessManagerprovidesalinkbetweentheSpatialServerandanydatasources.
FunctionsofArcIMSSpatialServerImagerendering–generatesmapimagesFeaturestreaming–streamsfeaturedataGeocoding–locatesaddressesonmapsQuery–returnsassociateddataforspatialandtabularqueriesDataextraction–returnsdatainShapefileformattotheclientArcIMSVirtualServerItisagroupingofoneormoreSpatialServers;itisnotaphysicalentity.
ItiscreatedtobettermanagedistributedSpatialServers.
ToimproveservicereliabilityandscalabilityFiveVirtualServers:ImageServer,FeatureServer,QueryServer,GeocodeServer,andExtractServer.
FeatureStreaming(Javaclientsonly)StreamsvectorsandattributesLocallycachedCompressedbinary/XMLJavaclientsLocalgeoprocessingBuffer,MapTips,Query,MapSymbolization,.
.
.
InternetFeatureStreamingThinClientvs.
ThickerClientThinClient-ImageStreamingServer-sideprocessingGIF/JPEG/PNGimagesFasterLoadingThickerClient-FeatureStreaming(javaonly)Vector/Raster/AttributeDataMoreClient-sideFunctionsRobustDevelopmentEnvironmentExamples:(howdotheysplitclient/servertasks,whatprotocolsareused,.
.
.
)RunningArcMaponthe37-312labmachinesRunningArcGISonMIT'sCitrixserverUsingtheMITOrthoServerviaabrowser(http://ortho.
mit.
edu)UsingtheMITOrthoToolsbuttonfromwithinArcMapRunningGoogleEarth(http://earth.
google.
com)TheMassGISdataviewer:Oliver(http://maps.
massgis.
state.
ma.
us/massgis_viewer/index.
htm)ShowninlabnextMonday:oArcIMSserverfor(optional)Lab#9(runningonaLinuxPC)o'IntelligentMiddleware'project:webservicesusingMinnesotaMapServer+PostgreSQLandPostGIS(runningonaLinuxPC)WrittenbyZhong-RenPeng,Fall,2003Lastmodified9November2005.
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