The advent of service-oriented architectures has strongly facilitated the development and deployment of largescale distributed applications. The middleware for orchestrating applications that consist of several distributed services has to be inherently distributed as well, in order to provide a high degree of scalability and to avoid any single point of failure. Self-healing execution of composite services requires replicated control metadata and instance data in a way that does not affect adaptivity and elasticity of the middleware. In this paper, we present OSIRIS-SR, a decentralized approach to self-healing composite service execution in a distributed environment. OSIRIS-SR exploits dedicated node monitors, organized in a self-organizing Safety Ring, for the replication of control data. Moreover, OSIRIS-SR leverages virtual stable storage for managing composite service instance data in a robust way. We present the architecture of OSIRIS-SR's Safety Ring and discuss how it provides self-healing composite service execution. The performance evaluation shows that the additional gain in robustness has only marginal effects on the scalability characteristics of the system.

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Abhandlungen grol~er kliniseher Gebiete durch eine einzelne SchuIe eigentfimlieh sind: Eine eigene .w.iderspruchsfreie Konzeption in fibersichtlicher, klarer, yon ~'-bersehneidungen freie Darstellung mit gelegentlichem Verzicht auf neue, noch nieht selbst geprfifte Theorien und Erfahrungen. Ein hervorragend lesbares Buch, das dam nephr01ogisch interessierten Arzt in Klinik und Praxis eine Ffille wertvolter Informationen vermittelt. H.P. WOLFf (Homburg/Saar) Tiehy, Hans: InIektion und Herdinfektion in der gheumatologie. (Der Rheumatisraus. }t~sg. yon RvDO~r SC~OE~,

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