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ISBN: 978-972-8939-25-0 © 2010 IADIS(SEMI-)AUTOMATIC NEGOTIATIONOF SERVICE LEVEL AGREEMENTSAnne Kümpel, Iris Braun, Josef Spillner and Alexander SchillChair of Computer NetworksTechnische Universität DresdenDresden, GermanyABSTRACTThe paper presents an approach to simplify and shorten the negotiation process towards a Service Level Agreement(SLA) between a web service provider and a service consumer. While interests of contract partners may differ in variousaspects, the negotiation phase can take a long time even without finding an optimal result. We propose an approach howthe negotiation phase can be shortened by using the decision matrices of the negotiation partners in a central component,which finds a quasi-optimal allocation for the negotiable parameters.KEYWORDSSOA, Web Service, Negotiation, SLA1. INTRODUCTIONIn the Internet of Services, where services become composable and tradable entities, contracts to describe theservice functionality and interfaces but also the obligations of service consumers and providers are anessential need. The negotiation phase of such contracts can be a complex and time consuming step in the lifecycle of service usage [Braun08]. Negotiations in general can be competitive or cooperative. While incompetitive negotiations every negotiator tries to maximize their own gain which implies several messageexchanges between all partners, the cooperative negotiation approach is interested in finding a global solutionfor all involved parties, which can be best reached through a mediator. The need of automating thenegotiation process especially in the service-oriented world has been discussed for more than ten years[Sierra97]. The approaches mainly are competitive, agent-based and follow an offer-counteroffer process. Acooperative approach, which uses a central component, is presented in [Comuzzi09]. They provide a pricedrivenconcept, whereas the generic concept presented in this paper is independent of monetary aspects. Theprice for a service can be subject of the negotiation process but also be negotiated or calculated afterwards.This approach can also be used for in-house service contracts or long term cross-service contracts.In the same context, researchers developed different mostly XML-based representations for servicecontracts. Prominent examples are WS-Agreement (WSAG) [wsag] and WSLA [wsla]. In the Internet ofServices, contracts, known as Service Level Agreements (SLA), exist between companies as well as betweenservice providers and end-users, who might have small knowledge of using agents or even of the creationprocess of SLAs. An SLA establishes agreements not only on the quality of a service (QoS) but also on allrelevant aspects of service usage between a service provider and a service consumer. A contract consists ofdifferent parts. While some of them are informative (e.g. provider address) and/or fixed (e.g. functionalaspects), others are variable and negotiable (e.g. support level, price or QoS parameters). To shorten the SLAnegotiation process, SLA templates, or QoS-profiles [Mulugeta07], are used to offer different profiles to theservice consumer. When there is no template that meets all consumers’ needs, they have to accept acompromise or must cancel the negotiation process. On the other hand if service providers often violateagainst the SLA, they have to delete or modify the templates to avoid violations in the future [Spillner09].The needs or business values for using or providing services normally differ between consumer and provider.While a consumer wants to have a short response time, the provider prefers to delay the guaranteed responsetime to save their resources. If only few parameters with little alternatives are negotiable, the easiest way is to282