Combining SLA prediction and cross layer adaptation for preventing SLA violations

Abstract. Service-based Applications (SBA) are deployed in highly dy-namic and distributed settings, where various parts of the constituent components- services and their infrastructure- are controlled by dif-ferent third parties. In such a loosely coupled environment, adaptation capabilities are needed to manage deviations and unforeseen situations which might lead to negative consequences (e.g. contractual penalties). Current approaches either focus on cross-layer-adaptation or the pre-vention of SLA violations. In contrast to this, the approach presented in this paper combines both. The paper presents an architecture as a generic framework for the management of arising problems during ser-vice execution. Multiple adaptation mechanisms are available to react on adaptation needs, acting on different layers of the SBA (including e.g. the composition layer and the infrastructure layer). The final goal of the cross-layer adaptation capability is to avoid the violation of agreed Service Level (in SLAs) and thus ensure the benefits of SBAs for both customers and providers.

Control flow requirements for automated service composition

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Optimizing monitorability of multi-cloud applications

When adopting a multi-cloud strategy, the selection of cloud providers where to deploy VMs is a crucial task for ensuring a good behaviour for the developed application. This selection is usually focused on the general information about performances and capabilities offered by the cloud providers. Less attention has been paid to the monitoring services although, for the application developer, is fundamental to understand how the application behaves while it is running. In this paper we propose an approach based on a multi-objective mixed integer linear optimization problem for supporting the selection of the cloud providers able to satisfy constraints on monitoring dimensions associated to VMs. The balance between the quality of data monitored and the cost for obtaining these data is considered, as well as the possibility for the cloud provider to enrich the set of monitored metrics through data analysis

Analysis and Verification of Service Interaction Protocols - A Brief Survey

Modeling and analysis of interactions among services is a crucial issue in Service-Oriented Computing. Composing Web services is a complicated task which requires techniques and tools to verify that the new system will behave correctly. In this paper, we first overview some formal models proposed in the literature to describe services. Second, we give a brief survey of verification techniques that can be used to analyse services and their interaction. Last, we focus on the realizability and conformance of choreographies.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330

Choreography Conformance Analysis: Asynchronous Communications and Information Alignment

Web service choreography languages provide a way to describe the collaboration protocol of multiple services that exchange information in order to achieve a common goal. This description may be seen as a specification that should be respected by the joint behavior of the set of services implementing the choreography. Such a conformance requires that (i) the observable behavior of the implementation corresponds to the behavior described by the protocol specification, and (ii) the business information is properly managed, guaranteeing that the participants have a shared knowledge about it, according to what is specified in the choreography. In this paper we present a choreography conformance analysis approach that addresses both the behavioral correspondence and the business information management. The key features of the approach are the capability to deal with asynchronous interactions and the ability to model and analyse the data managed and exchanged in the protocol, thus providing more accurate verification results. We also present symbolic techniques based on these formalizations that can be used for model checking of the choreography conformance

Modelling and Analysis of Time-related Properties in Web Service Compositions

In this paper we present an approach for modelling and analyzing time-related properties of Web service compositions defined as a set of BPEL4WS processes. We introduce a formalism, called Web Service Timed State Transition Systems (WSTTS), to capture the timed behavior of the composite web services. We also exploit an interval temporal logic to express complex timed assumptions and requirements on the system's behavior. Building on this formalization, we provide tools and techniques for model checking BPEL4WS compositions against time-related requirements. We perform a preliminary experimental evaluation of our approach and tools with the help of the e-Government case study

Analysis of Communication Models in Web Service Compositions

In this paper we describe an approach for the verification of Web service compositions dened by sets of BPEL processes. The key aspect of such a verification is the model adopted for representing the communications among the services participating in the composition. Indeed, these communications are asynchronous and buffered in the existing execution frameworks, while most verication approaches assume a synchronous communication model for efficiency reasons. In our approach, we develop a parametric model for describing Web service compositions, which allows us to capture a hierarchy of communication models, ranging from synchronous communications to asynchronous communications with complex buffer structures. Moreover, we develop a technique to associate with a Web service composition the most adequate communication model, i.e., the simplest model that is sufficient to capture all the behaviors of the composition. This way, we can provide an accurate model of a wider class of service composition scenarios, while preserving as much as possible an efficient performance in verification