W3CQoS服务模型.docx

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