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Validation of Service Level Agreements using Probabilistic Model Checking
With the fast growth of Information Technology (IT), organisations rely mostly on web services, cloud services and recently on Big Data Analytics services (BDA services), in order to support their business services. To securely use these services, service clients sign a Service Level Agreement (SLA) with service providers, regarding a particular service provision. Typically, SLAs define the properties that need to be preserved during the provision of a service (e.g., quality of service properties) and actions that will be applied if the service provision violates the defined properties (e.g., penalties or renegotiation). Whilst significant research has focused on monitoring SLAs during the provision of services, the exploration and validation of the potential consequences of SLAs for the involved parties prior to putting them in operation is not addressed by existing research. In this paper, we present an approach to SLA validation that is based model checking. Our approach is based on the translation of SLAs expressed in WSAgreement into models of the probabilistic model checker PRISM and the validation of SLA properties using the model checking capabilities of this tool
A framework for SLA-centric service-based Utility Computing
Nicht angegebenService oriented Utility Computing paves the way towards realization of service markets, which promise metered services through negotiable Service Level Agreements (SLA). A market does not necessarily imply a simple buyer-seller relationship, rather it is the culmination point of a complex chain of stake-holders with a hierarchical integration of value along each link in the chain.
In service value chains, services
corresponding to different partners are aggregated in a producer-consumer manner resulting in hierarchical
structures of added value. SLAs are contracts between service providers and service consumers, which ensure the expected Quality of Service (QoS) to different stakeholders at various levels in this hierarchy. \emph{This thesis addresses the challenge of realizing SLA-centric infrastructure to enable service markets for Utility Computing.}
Service Level Agreements play a pivotal role throughout the life cycle of service aggregation. The activities of service selection and service negotiation followed by the hierarchical aggregation and validation of services in service value chain, require SLA as an enabling technology. \emph{This research aims at a SLA-centric framework where the requirement-driven selection of services, flexible SLA negotiation, hierarchical SLA aggregation and validation, and related issues such as privacy, trust and security have been formalized and the prototypes of the service selection model and the validation model have been implemented. } The formal model for User-driven service selection utilizes Branch and Bound and Heuristic algorithms for its implementation. The formal model is then extended for SLA negotiation of configurable services of varying granularity in order to tweak the interests of the service consumers and service providers. %and then formalizing the requirements of an enabling infrastructure for aggregation and validation of SLAs existing at multiple levels and spanning % along the corresponding service value chains.
The possibility of service aggregation opens new business opportunities in the evolving landscape of IT-based Service Economy. A SLA as a unit of business relationships helps establish innovative topologies for business networks. One example is the composition of computational services to construct services of bigger granularity thus giving room to business models based on service aggregation, Composite Service Provision and Reselling. This research introduces and formalizes the notions of SLA Choreography and hierarchical SLA aggregation in connection with the underlying service choreography to realize SLA-centric service value chains and business networks. The SLA Choreography and aggregation poses new challenges regarding its description, management, maintenance, validation, trust, privacy and security. The aggregation and validation models for SLA Choreography introduce concepts such as: SLA Views to protect the privacy of stakeholders; a hybrid trust model to foster business among unknown partners; and a PKI security mechanism coupled with rule based validation system to enable distributed queries across heterogeneous boundaries. A distributed rule based hierarchical SLA validation system is designed to demonstrate the practical significance of these notions