W3CQoS服务模型.docx
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W3CQoS服务模型
QoSforWebServices:
RequirementsandPossibleApproaches
W3CWorkingGroupNote25November2003
Thisversion:
http:
//www.w3c.or.kr/kr-office/TR/2003/NOTE-ws-qos-20031125/
Latestversion:
http:
//www.w3c.or.kr/kr-office/TR/2003/ws-qos/
Previousversion:
ThisisthefirstversionofthisNote.
Editors:
KangChanLee,PEC,ElectronicsandTelecommunicationsResearchInstitute
JongHongJeon,PEC,ElectronicsandTelecommunicationsResearchInstitute
WonSeokLee,PEC,ElectronicsandTelecommunicationsResearchInstitute
Seong-HoJeong,HankukUniversityofForeignStudies
Sang-WonPark,HankukUniversityofForeignStudies
Abstract
Thisdocumentdescribesquality-of-service(QoS)requirementsforwebservices.Withtheproliferationofwebservicesasabusinesssolutiontoenterpriseapplicationintegration,theQoSforwebservicesisbecomingincreasinglyimportanttoserviceproviders.However,duetothedynamicandunpredictablecharacteristicsofthewebservices,itisnotaneasytasktoprovidethedesiredQoSforwebserviceusers.Furthermore,differentwebserviceapplicationswithdifferentQoSrequirementswillcompetefornetworkandsystemresourcessuchasbandwidthandprocessingtime.Nevertheless,anenhancedQoSforawebservicewillbringcompetitiveadvantageforserviceprovider.ToprovidesuchabetterQoS,itisfirstnecessarytoidentifyallthepossibleQoSrequirementsforwebservices,whichistheobjectiveofthisdocument.ThisdocumentalsodiscussespossibleapproachesforsupportingthewebserviceQoS.
StatusofthisDocument
Thissectiondescribesthestatusofthisdocumentatthetimeofitspublication.Otherdocumentsmaysupersedethisdocument.AlistofcurrentW3CpublicationsandthelatestrevisionofthistechnicalreportcanbefoundintheW3Ctechnicalreportsindexathttp:
//www.w3.org/TR/.
ThisisthefirstW3CNoteoftheWebServicesQoSRequirementsandPossibleApproachesdocument.
ItisachartereddeliverableoftheWebServicesArchitectureWorkingGroup,whichispartoftheWebServicesActivity.ThisNoterepresentstheWorkingGroup'sconsensusagreementastothecurrentsetofrequirementsfortheWebServicesArchitecture.TheWorkingGroupconsidersthisdocumenttobealivingdocumentandmayaddorchangetherequirementsastheanalysisofthearchitectureproceedsthroughtheWorkingGroup'sdeliberations.TheWorkingGrouprequestsfeedbackandcommentsonthisWorkingDraftfromtheWebservicescommunityandotherW3CWorkingGroups.
PublicationasaWorkingGroupNotedoesnotimplyendorsementbytheW3CMembership.Thisisadraftdocumentandmaybeupdated,replacedorobsoletedbyotherdocumentsatanytime.Itisinappropriatetocitethisdocumentasotherthanworkinprogress.PatentdisclosuresrelevanttothisNotemaybefoundontheMathWorkingGroup'spatentdisclosurepage.
TableofContents
QoSforWebServices:
RequirementsandPossibleApproaches1
Abstract2
StatusofthisDocument3
QoSRequirementsforWebServices5
1.Introduction5
1.1Performance5
1.2Reliability5
1.3Scalability6
1.4Capacity6
1.5Robustness6
1.6ExceptionHandling6
1.7Accuracy6
1.8Integrity7
1.9Accessibility7
1.10Availability7
1.11Interoperability7
1.12Security7
1.13Network-RelatedQoSRequirements8
2.PossibleApproachesforWebServiceQoSSupport10
2.1AnExtensiontoUDDI10
2.2AnExtensiontoSOAP10
2.3QoS-EnabledWebServiceCertification12
3.InteractionswithLowerLayerQoSMechanisms13
4.Summary14
5.References15
QoSRequirementsforWebServices
1.Introduction
TheQoSrequirementsforwebservicesheremainlyrefertothequalityaspectofawebservice.Thesemayincludeperformance,reliability,scalability,capacity,robustness,exceptionhandling,accuracy,integrity,accessibility,availability,interoperability,security,andnetwork-relatedQoSrequirements.Inthesubsequentsections,wedefineeachofthesequalityaspectsanddescribedesiredrequirements,basedonthevariousresearchefforts[1-11]inthisarea.
1.1Performance
Theperformanceofawebservicerepresentshowfastaservicerequestcanbecompleted.Itcanbemeasuredintermsofthroughput,responsetime,latency,executiontime,andtransactiontime,andsoon[2,4].
Throughputisthenumberofwebservicerequestsservedinagiventimeinterval.Responsetimeisthetimerequiredtocompleteawebservicerequest.Latencyistheround-tripdelay(RTD)betweensendingarequestandreceivingtheresponse.Executiontimeisthetimetakenbyawebservicetoprocessitssequenceofactivities.Finally,transactiontimerepresentsthetimethatpasseswhilethewebserviceiscompletingonecompletetransaction.Thistransactiontimemaydependonthedefinitionofwebservicetransaction.
Ingeneral,highqualitywebservicesshouldprovidehigherthroughput,fasterresponsetime,lowerlatency,lowerexecutiontime,andfastertransactiontime.
1.2Reliability
Webservicesshouldbeprovidedwithhighreliability.Reliabilityhererepresentstheabilityofawebservicetoperformitsrequiredfunctionsunderstatedconditionsforaspecifiedtimeinterval[10].Thereliabilityistheoverallmeasureofawebservicetomaintainitsservicequality.Theoverallmeasureofawebserviceisrelatedtothenumberoffailuresperday,week,month,oryear.Reliabilityisalsorelatedtotheassuredandordereddeliveryformessagesbeingtransmittedandreceivedbyservicerequestorsandserviceproviders[4].
1.3Scalability
Webservicesshouldbeprovidedwithhighscalability.Scalabilityrepresentsthecapabilityofincreasingthecomputingcapacityofserviceprovider'scomputersystemandsystem'sabilitytoprocessmoreusers'requests,operationsortransactionsinagiventimeinterval[2].Itisalsorelatedtoperformance.Webservicesshouldbescalableintermsofthenumberoperationsortransactionssupported.
1.4Capacity
Webservicesshouldbeprovidedwiththerequiredcapacity.Capacityisthelimitofthenumberofsimultaneousrequestswhichshouldbeprovidedwithguaranteedperformance[2].Webservicesshouldsupporttherequirednumberofsimultaneousconnections.
1.5Robustness
Webservicesshouldbeprovidedwithhighrobustness.Robustnesshererepresentsthedegreetowhichawebservicecanfunctioncorrectlyeveninthepresenceofinvalid,incompleteorconflictinginputs[2].Webservicesshouldstillworkevenifincompleteparametersareprovidedtotheservicerequestinvocation.
1.6ExceptionHandling
Webservicesshouldbeprovidedwiththefunctionalityofexceptionhandling.Sinceitisnotpossiblefortheservicedesignertospecifyallthepossibleoutcomesandalternatives(especiallywithvariousspecialcasesandunanticipatedpossibilities),exceptionsshouldbehandledproperly[2].Exceptionhandlingisrelatedtohowtheservicehandlestheseexceptions.
1.7Accuracy
Webservicesshouldbeprovidedwithhighaccuracy.Accuracyhereisdefinedastheerrorrategeneratedbythewebservice[2].Thenumberoferrorsthattheservicegeneratesoveratimeintervalshouldbeminimized.
1.8Integrity
Integrityforwebservicesshouldbeprovidedsothatasystemorcomponentcanpreventunauthorizedaccessto,ormodificationof,computerprogramsordata.Therecanbetwotypesofintegrity:
dataintegrityandtransactionalintegrity.Dataintegritydefineswhetherthetransferreddataismodifiedintransit.Transactionalintegrityreferstoaprocedureorsetofprocedures,whichisguaranteedtopreservedatabaseintegrityinatransaction[4].
1.9Accessibility
Webservicesshouldbeprovidedwithhighaccessibility.Accessibilityhererepresentswhetherthewebserviceiscapableofservingtheclient'srequests[4].Highaccessibilitycanbeachieved,e.g.,bybuildinghighlyscalablesystems.
1.10Availability
Thewebserviceshouldbeready(i.e.,available)forimmediateconsumption.Thisavailabilityistheprobabilitythatthesystemisupandrelatedtoreliability[11].Time-to-Repair(TTR)isassociatedwithavailability.TTRrepresentsthetimeittakestorepairthewebservice[4].Theserviceshouldbeavailableimmediatelywhenitisinvoked.
1.11Interoperability
Webservicesshouldbeinteroperablebetweenthedifferentdevelopmentenvironmentsusedtoimplementservicessothatdevelopersusingthoseservicesdonothavetothinkaboutwhichprogramminglanguageoroperatingsystemtheservicesarehostedon[4].
1.12Security
Webservicesshouldbeprovidedwiththerequiredsecurity.WiththeincreaseintheuseofwebserviceswhicharedeliveredoverthepublicInternet,thereisagrowingconcernaboutsecurity.Thewebserviceprovidermayapplydifferentapproachesandlevelsofprovidingsecuritypolicydependingontheservicerequestor.
Securityforwebservicesmeansprovidingauthentication,authorization,confidentiality,traceability/auditability,dataencryption,andnon-repudiation.Eachoftheseaspectsisdescribedbelow[2,4].
●Authentication:
Users(orotherservices)whocanaccessserviceanddatashouldbeauthenticated.
●Authorization:
Users(orotherservices)shouldbeauthorizedsothattheyonlycanaccesstheprotectedservices.
●Confidentiality:
Datashouldbetreatedproperlysothatonlyauthorizedusers(orotherservices)canaccessormodifythedata.
●Accountability:
Thesuppliercanbeholdaccountablefortheirservices.
●TraceabilityandAuditability:
Itshouldbepossibletotracethehistoryofaservicewhenarequestwasserviced.
●Dataencryption:
Datashouldbeencrypted.
●Non-Repudiation:
Ausercannotdenyrequestingaserviceordataafterthefact.Thes