The KLU faculty, post-docs, and PhD candidates regularly publish the results of their research in scientific journals. You will find a complete overview of all KLU publications below (e.g. articles in peer-reviewed journals, professional journals, books, working papers, and conference proceedings). Search for relevant terms and keywords, or filter the list by name, year of publication or type of publication. The references include DOIs and abstracts where available, and you can download them to your own reference database or platform. We regularly update the database with new publications.

Book Chapters

Copy reference link   DOI: 10.1007/978-3-540-78617-7_5

Abstract: Service composition enables the creation of services previously unavailable through the aggregation of existing services. The result is called a service composition. Exposing a service composition as a service, the result is called a composed service. It can be distinguished from atomic services. Service composition approaches can be differentiated along two axes: point in time of composition and degree of automation. With design-time and run-time we can identify two different points in time for doing a composition. Additionally we can distinguish between three different degrees of automation: manual, assisted, and automated service composition.

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Copy reference link   DOI: 10.1007/978-3-540-89652-4_56

Abstract: Service provisioning is largely built on agreements specifying the mutual responsibilities of service providers and their customers with respect to functional and non-functional parameters. Current SLA management approaches, i.e. WSLA, WS-Agreement, or WSOL, provide extensive SLA language formalizations and management frameworks. However, they focus on bi-lateral service requester/provider constellations neglecting the SLA management requirements of composite service providers, i.e. managing SLAs with atomic service providers and with composite service requesters and aligning both with each other. A SLA management solution for composite services has to consider the contribution of sourced services - formalized in their (atomic) SLAs (ASLA) - in the management of the provided service - formalized in its respective (composite) SLA (CSLA). This paper presents the novel COmposite Sla MAnagement (COSMA) approach for an integrated management of atomic and composite SLAs during their entire lifecycle. It can be utilized for controlling the relationships between ASLAs/CSLAs and thus serves as the basis for managing and optimizing the SLAs involved in composite services.

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Abstract: Service compositions enable users to realize their complex needs as a single request. Despite intensive research, especially in the area of business processes, web services and grids, an open and valid question is still how to manage service compositions in order to satisfy both functional and non-functional requirements as well as adapt to dynamic changes. In this paper we describe an approach towards adaptive management of QoS-aware service compositions. This approach integrates well known concepts and techniques and proposes various execution strategies based on dynamic selection and negotiation of services, contracting based on service level agreements, service enactment with flexible support for exception handling, monitoring of service level objectives, and profiling of execution data.

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Copy reference link   DOI: 10.1007/11948148_61

Abstract: Service compositions enable users to realize their complex needs as a single request. Despite intensive research, especially in the area of business processes, web services and grids, an open and valid question is still how to manage service compositions in order to satisfy both functional and non-functional requirements as well as adapt to dynamic changes. In this paper we propose an (functional) architecture for adaptive management of QoS-aware service compositions. Comparing to the other existing architectures this one offers two major advantages. Firstly, this architecture supports various execution strategies based on dynamic selection and negotiation of services included in a service composition, contracting based on service level agreements, service enactment with flexible support for exception handling, monitoring of service level objectives, and profiling of execution data. Secondly, the architecture is built on the basis of well know existing standards to communicate and exchange data, which significantly reduces effort to integrate existing solutions and tools from different vendors. A first prototype of this architecture has been implemented within an EU-funded Adaptive Service Grid project.

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Abstract: Existing multivariate generalized autoregressive conditional heteroskedasticity (GARCH) models either impose strong restrictions on the parameters or do not guarantee a well-defined (positive-definite) covariance matrix. I discuss the main multivariate GARCH models and focus on the BEKK model for which it is shown that the covariance and correlation is not adequately specified under certain conditions. This implies that any analysis of the persistence and the asymmetry of the correlation is potentially inaccurate. I therefore propose a new Flexible Dynamic Correlation (FDC) model that parameterizes the conditional correlation directly and eliminates various shortcomings. Most importantly, the number of exogenous variables in the correlation equation can be flexibly augmented without risking an indefinite covariance matrix. Empirical results of daily and monthly returns of four international stock market indices reveal that correlations exhibit different degrees of persistence and different asymmetric reactions to shocks than variances. In addition, I find that correlations do not always increase with jointly negative shocks implying a justification for international portfolio diversification.

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