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Abstract : |
Epsilon serializability (ESR) is a weaker form of correctness designed to provide more concurrency than classic serializability (SR) by allowing, for example, query transactions to view inconsistent data in a controlled fashion i:e: limiting the inconsistency within the specified bounds. In the previous literature on ESR, inconsistency bounds have been specified with respect to transactions or with respect to objects. In this paper, we introduce the notion of hierarchical inconsistency bounds that allows inconsistency to be specified at different granularities. The motivation for this comes from the way data is usually organized, in hierarchical groups, based on some common features and interrelationships. Bounds on transactions are specified at the top of the hierarchy, while bounds on the objects are specified at the bottom and on groups in between. We also discuss mechanisms needed to control the inconsistency so that it lies within the specified bounds. While executing a transaction, the system checks for possible violation of inconsistency bounds bottom up, starting with the object level and ending with the transaction level. Thus far, to our knowledge, no work has been done to determine the quantitative performance improvement resulting from ESR. Hence in this paper we report on an evaluation of the performance, |
