Publications in Service Level Agreement

Articles in Refereed Journals:

1. D. Ardagna, M. Comuzzi, E. Mussi, B. Pernici, P. Plebani. PAWS: A Framework for Executing Adaptive Web-Service Processes. IEEE Software, To Appear, 2007.
   Abstract: The processes with adaptive Web services framework couples design-time and runtime mechanisms to flexibly and adoptively execute managed Web-services-based business processes.

2. Giorgia Lodi, Fabio Panzieri, Davide Rossi, Elisa Turrini. SLA-Driven Clustering of QoS-Aware Application Servers. IEEE Trans. Software Eng., Vol. 33, Num. 3, pages 186-197, 2007.
   Abstract: In this paper, we discuss the design, implementation, and experimental evaluation of a middleware architecture for enabling service level agreement (SLA)-driven clustering of QoS-aware application servers. Our middleware architecture supports application server technologies with dynamic resource management: application servers can dynamically change the amount of clustered resources assigned to hosted applications on-demand so as to meet application-level quality of service (QoS) requirements. These requirements can include timeliness, availability, and high throughput and are specified in SLAs. A prototype of our architecture has been implemented using the open-source J2EE application server JBoss. The evaluation of this prototype shows that our approach makes possible JBoss' resource usage optimization and allows JBoss to effectively meet the QoS requirements of the applications it hosts, i.e., to honor the SLAs of those applications.

3. Wenhui Sun, Jinyu Zhang, Feng Liu. WS-SLA: A Framework for Web Services Oriented Service Level Agreements. Computer Supported Cooperative Work in Design, 2006. CSCWD '06. 10th International Conference on, To Appear, May 2006.
   Abstract: Service level agreements (SLA) becomes the prevailing business model for delivery of a large number of products and services in telecommunication and IT arenas. We presents an integrated service level agreement model applied to operating supporting system (OSS), on the basis of WfMC workflow reference model and service oriented architecture (SOA). And an application scenario instance of SLA system architecture is described by a set of operations models by Business Process Execution Language (BPEL)

4. Alexander Keller, Heiko Ludwig. The WSLA Framework: Specifying and Monitoring Service Level Agreements for Web Services. J. Network Syst. Manage., Vol. 11, Num. 1, 2003.
   Abstract: We describe a novel framework for specifying and monitoring Service Level Agreements (SLA) for Web Services. SLA monitoring and enforcement becomes increasingly important in a Web Service environment where enterprises rely on services that may be subscribed dynamically and on demand. For economic and practical reasons, we want an automated provisioning process for both the service itself as well as the SLA management system. It measures and monitors the QoS parameters, checks the agreed-upon service levels, and reports violations to the authorized parties involved in the SLA management process. The Web Service Level Agreement (WSLA) framework, our approach to these issues, is targeted at defining and monitoring SLAs for Web Services. Although WSLA has been designed for a Web Services environment, it is applicable as well to any inter-domain management scenario such as business process and service management or the management of networks, systems and applications in general. The WSLA framework consists of a flexible and extensible language based on XML Schema and a runtime architecture comprising several SLA monitoring services, which may be outsourced to third parties to ensure a maximum of accuracy. WSLA enables service customers and providers to unambiguously define a wide variety of SLAs, specify the SLA parameters and the way how they are measured, and relate them to managed resource instrumentations. Upon receipt of an SLA specification, the WSLA monitoring services are automatically configured to enforce the SLA. An implementation of the WSLA framework, the SLA Compliance Monitor, is publicly available as part of the IBM Web Services Toolkit.

Articles in Refereed Conferences:

1. Cinzia Cappiello, Marco Comuzzi, Pierluigi Pleban. On Automated Generation of Web Service Level Agreements . Advanced Information Systems Engineering, Vol. 4495, Springer Verlag, June 2007.
   Abstract: Before a service invocation takes place, an agreement between the service provider and the service user might be required. Such an agreement is the result of a negotiation process between the two parties and defines how the service invocation has to occur. Considering the Service Oriented Computing paradigm, the relationship among providers and users is extremely loose. Traditional agreements are likely to concern long term relationships and to be manually performed. In this paper, we propose a model to generate service level agreement on-the-fly. Just before the invocation commences, the quality of the service is negotiated in order to generate a service level agreement tied to that specific invocation. Such an approach relies on a quality model that supports both users requirements and providers capabilities definition.

2. Elisabetta Di Nitto, Massimiliano Di Penta, Alessio Gambi, Gianluca Ripa, Maria Luisa Villani. Negotiation of Service Level Agreements: An Architecture and a Search-Based Approach. ICSOC, pages 295-306, 2007.
   Abstract: Software systems built by composing existing services are more and more capturing the interest of researchers and practitioners. The envisaged long term scenario is that services, offered by some competing providers, are chosen by some consumers and used for their own purpose, possibly, in conjunction with other services. In the case the consumer is not anymore satisfied by the performance of some service, he can try to replace it with some other service. This implies the creation of a global market of services and poses new requirements concerning validation of exploited services, security of transactions engaged with services, trustworthiness, creation and negotiation of Service Level Agreements with these services. In this paper we focus on the last aspect and present our approach for negotiation of Service Level Agreements. Our architecture supports the actuation of various negotiation processes and offers a search-based algorithm to assist the negotiating parts in the achievement of an agreement.

3. Mohan Baruwal Chhetri, Jian Lin, SukKeong Goh, Jian Ying Zhang, Ryszard Kowalczyk, Jun Yan. A Coordinated Architecture for the Agent-based Service Level Agreement Negotiation ofWeb Service Composition. ASWEC, pages 90-99, 2006.
   Abstract: Recent progress in the field of Web services has made it possible to integrate inter-organizational and heterogeneous services on the Web at runtime. If a user request cannot be satisfied by a single Web service, it is (or should be) possible to combine existing services in order to fulfill the request. However, there are several challenging issues that need to be addressed before this can be realized in the true sense. One of them is the ability to ensure end-to-end QoS of a Web service composition. There is a need for a SLA negotiation system which can ensure the autonomous QoS negotiation of Web service compositions irrespective of the application domain. In this paper we propose agent-based coordinated-negotiation architecture to ensure collective functionality, end-to-end QoS and the stateful coordination of complex services. We describe a prototype implementation to demonstrate how this architecture can be used in different application domains. We have also demonstrated how the negotiation system on the service provider's side can be implemented both as an agent based negotiation system and as a Web service based negotiation system.

4. Nicole Oldham, Kunal Verma, Amit Sheth, Farshad Hakimpour. Semantic WS-agreement partner selection. WWW '06: Proceedings of the 15th international conference on World Wide Web, pages 697-706, ACM, 2006.
   Abstract: In a dynamic service oriented environment it is desirable for service consumers and providers to offer and obtain guarantees regarding their capabilities and requirements. WS-Agreement defines a language and protocol for establishing agreements between two parties. The agreements are complex and expressive to the extent that the manual matching of these agreements would be expensive both in time and resources. It is essential to develop a method for matching agreements automatically. This work presents the framework and implementation of an innovative tool for the matching providers and consumers based on WS-Agreements. The approach utilizes Semantic Web technologies to achieve rich and accurate matches. A key feature is the novel and flexible approach for achieving user personalized matches.

5. Rocco De Nicola, Gianluigi Ferrari, Ugo Montanari, Rosario Pugliese, Emilio Tuosto. A Basic Calculus for Modelling Service Level Agreements. International Conference on Coordination Models and Languages, LNCS, Vol. 3454, pages 33-48, Springer Verlag, April 2005.
   Abstract: The definition of suitable abstractions and models for identifying, understanding and managing Quality of Service (QoS) constraints is a challenging issue of the Service Oriented Computing paradigm. In this paper we introduce a process calculus where QoS attributes are first class objects. We identify a minimal set of primitives that allow capturing in an abstract way the ability to control and coordinate services in presence of QoS constraints.

6. James Skene, D. Davide Lamanna, Wolfgang Emmerich. Precise Service Level Agreements. ICSE, pages 179-188, 2004.
   Abstract: SLAng is an XML language for defining service level agreements, the part of a contract between the client and provider of an Internet service that describes the quality attributes that the service is required to possess. We define the semantics of SLAng precisely by modelling the syntax of the language in UML, then relating the language model to a model that describes the structure and behaviour of services. The presence of SLAng elements imposes behavioural constraints on service elements, and the precise definition of these constraints using OCL constitutes the semantic description of the language. We use the semantics to define a notion of SLA compatibility, and an extension to UML that enables the modelling of service situations as a precursor to analysis, implementation and provisioning activities.

Technical Reports and Manuals:

1. Alain Andrieux, Karl Czajkowski, Asit Dan, Kate Keahey, Heiko Ludwig, Toshiyuki Nakata, Jim Pruyne, John Rofrano, Steve Tuecke, Ming Xu. Web Services Agreement Specification (WS-Agreement). Grid Resource Allocation Agreement Protocol, September 2005.
   Abstract: This document describes Web Services Agreement Specification (WS-Agreement), a Web Services protocol for establishing agreement between two parties, such as between a service provider and consumer, using an extensible XML language for specifying the nature of the agreement, and agreement templates to facilitate discovery of compatible agreement parties. The specification consists of three parts which may be used in a composable manner: a schema for specifying an agreement, a schema for specifying an agreement template, and a set of port types and operations for managing agreement life-cycle, including creation, expiration, and monitoring of agreement states.

2. Heiko Ludwig, Alexander Keller, Asit Dan, Richard P. King, Richard Franck . Web Service Level Agreement (WSLA) Language Specification. IBM Corporation, 2003.
   Abstract: This document describes the specification language for service level agreements for Web Services, the Web Service Level Agreement (WSLA) language. WSLAs are agreements between a service provider and a customer and as such define the obligations of the parties involved. Primarily, this is the obligation of a service provider to perform a service according to agreed-upon guarantees for IT-level service parameters (such as availability, response time and throughput) for Web Services.
   An SLA also specifies the measures to be taken in case of deviation and failure to meet the asserted service guarantees, for example, a notification of the service customer. The assertions of the service provider are based on a detailed definition of service parameters including the algorithms - how basic metrics should be measured in systems and how they are aggregated into composite metrics and SLA parameters. In addition, a WSLA can express the operations of monitoring and managing the service. This may include third parties (such as Management Service Providers) that contribute to the measurement of metrics, supervision of guarantees or even the management of deviations of service guarantees. These multi-party constellations necessitate the definition of the interactions among the parties supervising the WSLA.
   However, a WSLA only covers the agreed common view of a service between the parties involved. To actually act as a participant in a WSLA, parties have various degrees of freedom to define an implementation policy for a service and its supervision. Typically, the obligations of a WSLA must be translated into system-level configuration information, which can be proprietary to each party involved.

3. Akhil Sahai, Anna Durante, Vijay Machiraju. Towards Automated SLA Management for Web Services. Num. HPL-2001-310, HP Laboratories, July 2002.
   Abstract: In order to automate SLA management it is essential to specify SLAs in precise and unambiguous manner as well as keep the specification flexible. While precision will help automate the process of monitoring and metric collection, flexibility will enable extending it to unforeseen service level agreement specifications.