frameworkfor webservices orientedservice level...

Proceedings of the 10th International Conference on Computer Supported Cooperative Work in Design

WS-SLA: A Framework for Web Services Oriented Service Level Agreements

Wenhui Sun, Jinyu Zhang, Feng LiuCollege ofcomputer and information technologyBeijing Jiaotong University, Beijing, 100044, China

wenhuisong@netone. net. cn

Abstract

Service level agreements (SLA) becomes the prevailingbusiness modelfor delivery ofa large number ofproductsand services in telecommunication and IT arenas. Wepresents an integrated service level agreement modelapplied to operating supporting system (OSS), on thebasis of WfMC workflow reference model and serviceoriented architecture (SOA). And an application scenarioinstance ofSLA system architecture is described by a setofoperationsmodels by Business Process Execution Language (BPEL).

Keywords: Service level agreements, BPEL, SOA, OSS

1. Introduction

A service level agreement(SLA)E'l is a contract or

agreement that formalizes a business relationship, or partof the relationship, between two parties. Most often ittakes the form of a negotiated contract made between a

service provider and a customer and defines a price paidin exchange for an entitlement to a product or service tobe delivered under certain terms, conditions, and withcertain financial guarantees. Service level management isa method for a service provider to attract a customer andis applied to OSS application. So it is a hot research topicto design a framework of SLA driven OSS.

The Workflow Management Coalition (WfMC)E21defines workflow as the automation of a business process,in whole or part, during which documents, information or

tasks are passed from one participant to another for action,according to a set of procedural rules. Workflowmanagement system defines, create and manages theexecution of workflows through the use of software,running on one or more workflow engines, which is ableto interpret the process definition, interact with workflowparticipants and, where required, invoke the use of ITtools and applications. At present most work on workflowmanagement focus on workflow management systemitself and its software realization. It is a recent hotresearch topic to combine workflow management andservice management.

Service oriented architecture (SOA) is a systemarchitecture to integrate autonomous distributed

components. The components are loosely coupled witheach other by strictly-typed interfaces and standardizedcommunication protocols. Service-oriented architecture(SOA) allows dynamic service discovery, binding,execution, monitoring, and evaluation. Web Services isan example of SOA and it uses a variety of standardizedprotocols such as UDDI, SOAP, WSDL. At present mostresearch work on SOA focus on web service compositionsuch as BPEL 51, BPEL4WS 6] and WS-Transaction7],which are all XML-based flow languages that defineshow business process interact within or betweenenterprises. The aim of this paper is to study how SOA isapplied to implementation of a framework of SLA drivenOSS.

The remainder of this paper is organized as follows. InSection 2, we propose implementation of a framework ofservice level agreements based on workflow management.And we discuss each component and its function of theframework of service level agreements. In Section 3, byusing Business Process Execution Language (BPEL) ofSOA, we present an application scenario instance of SLAsystem architecture. In Section 4, the conclusion andfuture research directions will be given.

2. A framework of service level agreementsbased on workflow management

At present almost all of SLA implementation are basedon TMF's SLA handbook blueprintE'l.There are twodifferent approaches to implementing an SLA model,which stem from differences in company focus and fromthe product suites. One is customer-centric in the sensethat it deals with customers, contracts, and billing cycles.For example, Amdoces's SLA blueprintE'l is such aproduct. The second is network-focused and deals withquality of service metrics, network fault tolerance such asMicromuse's Netcool suite and Orchestream's Resolvesuite. These two approaches focus on customer-centricand network performance-oriented respectively. Mergingthese two approaches should be provided to implement aintegrated SLA management. In addition, no matter whatthe model is customer-centric or network performanceoriented, an effective business process management is putinto implementation of SLA framework. We propose anintegrated SLA model, which is based on the author's

1-4244-0165-8/06/$20.00 C 2006 IEEE.


belief that the only way to drive efficiency and ensureQuality of Service (QoS) commitments are consistentlymet is to drive the business processes directly from theSLA definitions. The integrated SLA framework is builton distributed computing technology, workflowtechnology, business intelligence and portal technology.

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The Integrated service level agreement framework isdivided into five layers: a integration layer, an automationlayer, a collaboration layer, an intelligence layer and auniversal access layer.

The framework of the integrated SLA is shown inFigure 1.

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Figure 1. The Integrated Service Level Agreement framework

2.1 Integration layer

The environment must bring together participants,applications, processes, and interfaces seamlessly into a

common management environment. Integration occurs atfour levels: (I)organizational, (2)process, (3)datainterchange, and (4)the collaborative level, whichcombines the integration of the other levels into a singlework flow. Furthermore, the data integration is made upof both technical and semantic aspects.

In a distributed environment, each component or

system functions in an autonomous manner need tointeract with each other in order to satisfy the end-to-endprocesses handled by the OSS. Interaction between thesesystems normally follows one of three primary paradigms:an invocation paradigm, a messaging paradigm, or a

publish-subscribe paradigm. The first common paradigmis a invocation paradigm. In a invocation paradigm one

system needs a service that has been implemented withinanother system. The system that implements the servicedefines how calls are made to activate this service.Examples include CORBA

invocations and XML-based invocations such as SOAP.The second common paradigm is message-orientedmiddleware(MOM). Products supporting this paradigmmanage the transfer of messages from one system toanother using a messaging bus. This mode is often calledstore-and-forward. The third common paradigm ispublish-subscribe. This paradigm is based on the conceptof a business event.

2.2 Automation layer

Workflow is the computerized facilitation orautomation of a business process, in whole or part. Whileworkflow may be manually organized, in practice mostworkflow is normally organized within the context of anIT system to provide computerized support for theprocedural automation. A system that completely defines,manages and executes "workflows" through the executionof software whose order of execution is driven by acomputer representation of the workflow logic, which isgranted as Workflow Management System.

The Workflow Reference model has been developedfrom the generic workflow application structure byidentifying the interfaces within this structure which


enable products to interoperate at a variety of levels. Allworkflow systems contain a number of genericcomponents which interact in a defined set of ways.These generic components are process definition tools,workflow enactment service, invoked applications,workflow client applications, and administration andmonitoring.

2.3 Collaboration layer

The environment must support many differententities and parties working together in series, parallel, orin a combined manner. Collaboration too requires theability to seamlessly support both human and electronicparticipation in collaborative efforts. Collaborationcontrols the execution of each individual system andmanages dataflow among each individual system.Monitoring system of collaboration layer subscribesevents produced by every individual system and produceshigh-level information. QoS management of collaborationlayer deals with cost, performance, security, availabilityand scalability. Grid computing and Service orientedarchitecture is closely related to distributed applicationintegration and collaboration domain. The aim of gridcomputing is to collaborate among a variety of resourcesto solve complicated scientific problems. Service orientedarchitecture is a new integration paradigm which focuseson service composition.

2.4 Intelligence layer

The environment must provide very high levels ofappropriate SLA compliance and other businessintelligence to community members. Intelligence maytake the form of real-time or periodic workflowmonitoring, key performance indicators, monitors, orreports. The systems within the environment must alsofunction within the work flow and be able to recognizethreshold violations and subsequently initiate task

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generation or trigger automation of predefined actions,such as notifications, escalations, queries, and so on.Business intelligence is actually a integrated applicationof data warehouse, OLAP and data mining.

2.5 Universal access layer (Portal layer)

The concept that all participants involved in any workflow, both human and electronic, must be able to securelyaccess the environment in a convenient user-friendlymanner. The portal provides the following functionswhich allow users to make these OSS applicationsefficiently by using our workflow-based portal.User Authentication and Profile: This is basiccomponents for a portal. A user is authenticated only onceand provided all functions of our portal.Graphic Workflow Editor: User can describe a workflowby graphical tool or text-based XML editor. Firstactivities and its input/output data are defined. Second,User describes the interaction between them by making aworkflow with them.Workflow Execution: When workflow is running, thisshows the state of executed workflow graphically. Theexecution of an activity, state of input/output data transfer,values of some variables in workflow, and standardoutput/error of a running activity are displayed.Resource Information: Resource Information functionenables us to find data and status about resources such asCPU, memory, network, OS.

3. Application scenario instance of SLAsystem architecture

The SLA life cycle consists of the phases: SLAdevelopment, negotiation and sales, implementation,execution, assessment. The Telemanagement Forum sservice level agreement life cycle is shown in Fig. 2.

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D6 ioptemoIat6s Nlegofie and. Generte and Operate and1 S4nd 6it:tanents Mooeu C(NOW8 proislion sefce Ma intain (O&M), anlld assess

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Figure 2. The Tele management Forum's service level agreements life cycle

The high-level flow of SLA-driven OSS applicationcan be captured in BPEL of service oriented architectureshown in Fig. 3. The high-level flow of SLA life cycle

starts from developing contracts, negotiating contracts,then moves to implementing contracts, monitoringcontracts, and ends with assessing contracts.


<process name="slaDrivenProcess"targetNamespace=http://ws-sla.com/ws-bp/ws-slaxmlns=http://schemas.xmlsoap.org/ws/2003/03/business-

process/xmlns:lns=http://ws-sla.org/wsdl/ws-sla>

<sequence><receive partnerLink="Customers"

portType="Ins:ws-sla"operation="sendServiceRequirements"variable="ServiceRequirements">

</receive><flow><sequence><invoke portType="Ins:DevelopContract"

operation="requestDevelop"></invoke><invoke portType="Ins:NegotiateContract"

operation="requestNegotiate"></invoke><invoke portType="Ins:ImplementationContract"

operation="requestlmplementation"></invoke><invoke portType="Ins:MonitorContract"

operation="requestMonitor" ></invoke><invoke portType="Ins:AssessContract"

operation="requestAssess"></invoke></flow><reply partnerLink="Customers"

portType="Ins:ws-sla"operation="sendServiceRequirements"/>

</sequence>Fig. 3: High-level SLA life cycle in BPEL

For more comprehensive discussion, we introduceexample scenarios of SLA driven OSS. In this examplewe suppose a SLA framework consisting of two modules:SLA service management system and networkmanagement system support SLA service managementsystem. SLA service management system is composed ofthree sub modules: contract creation, contract negotiationand contract implementation. We collect data from SNMPnetwork management system to monitoring the executionof contracts. We wrap SNMP API into web services.Management interface can be obtained by applying theSNMP MIB to XML Translation algorithmE8'. In this casethe produced interface is fine-grained. However we take acoarse-grained interface module. Given the SNMP MIBdefinition, we map each SMIv2 MIB table object into T-style interfaces and all remaining scalar objects into S-style interfaces. SNMP get operation for scalar objectscan be implemented with WSDL. Interface of webservices shown in Fig. 4.

<wsdl: definitionstargetNamespace=http //ws-sla.com/getentryxmlns:wsdl=http //schemas.xmlsoap.or/wsdl/xmlns:xs=h w.w.

xmlns :tns=http //ws-sla.com/getentry

... <wsdl:types><xs:schema><xs:import

namespace=http:Hws-sla.com/getentryschemalocation="... "/>

</xs:schema></wsdl:types>

... <wsdl:portType name="getentry"><operation name="getentry" ...

</wsdl:portType>

</wsdl:definitions>Fig.4: SNMP get operation for scalar objects in WSDL

4. Conclusion and Future Work

In this paper, we propose a framework of servicelevel agreements based on workflow management. Wealso present an application scenario instance of SLAsystem architecture by using Business Process ExecutionLanguage (BPEL) of service oriented architecture. Theframework can accomplish automation of businessprocess of SLA-driven OS and provide flexibility of anddynamics of service management. It can adapt toscalability of new services and make service managementefficiently. At present the framework has bee applied tothe implementation of the prototype of Hi-technologysoftware incubator platform project (863 project).What we do next is to take advantage of the design idea

of service oriented architecture and BEA's and IBM'sbusiness process integration development tools andimplement a product of SLA driven OSS.

References[1] Lee John J, Ben-Natan Ron, Integrating service levelagreements with OSS, Wiley Publshing, 2002[2] WfMC TC00-1003, The Workflow Reference Model, 1995[3]Watanabe T, "Agent-oriented model for managing long-livedtransaction, based on workflow and task graph", ComputationalIntelligence and Multimedia Application, New Delhi, India,1999[4]Cai XiaoLu, Liang YuQi, Web services technology,architecture and application, Electronic Industry Press, 2002[5]Business Process Execution Language for Web ServicesSpecification, version 1.1, available at:http://www 106.ibm.com/developerworks/webservices/library/ws-bpel/[6]Wang X.,Yue K.,Huang J.,Zhou A.,"Service selection fordynamic-driven Web services processing", Proceedings of theICWS 2004, San Diego, California, USA, 2004[7]Yue Kun, Wang Xiaoling, Zhou Aoying, "An overview: Webservices core technology", Journal ofSoftware, 2004, 15(3)[8]Jeong-Hyuk Yoon, Hong-Taek Ju and James W. Hong,"Development of SNMP-XML translator and gateway for XML-based integrated network management", Internationaljournal ofnetwork management 2003; 13

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