document: Survivability-oriented self-tuning of web systems Running in a highly uncertain and changing environment , Web systems can not always provide full set of services with optim ¬ al quality , especially when the workload is high or failures in subsys-tems occur frequently . It is thus desirable to continuously maintain a high satisfaction level of the system value proposition , hereafter survivability assurance , while relaxing\/sacrificing certain quality\/functional requirements that are not crucial to the survival of the Web systems . In this paper , we propose a requirements-driven self-tuning method for survivability assurance of Web systems . Using a value-based feedback controller plus a requirements-oriented reasoner , our method makes both quality and functional requirements tradeoffs decisions at runtime .
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