Biblio

Repairing erroneous or conflicting data that violate a set of constraints is an important problem in data management. Many automatic or semi-automatic data-repairing algorithms have been proposed in the last few years, each with its own strengths and weaknesses. Bart is an open-source error-generation system conceived to support thorough experimental evaluations of these data-repairing systems. The demo is centered around three main lessons. To start, we discuss how generating errors in data is a complex problem, with several facets. We introduce the important notions of detectability and repairability of an error, that stand at the core of Bart. Then, we show how, by changing the features of errors, it is possible to influence quite significantly the performance of the tools. Finally, we concretely put to work five data-repairing algorithms on dirty data of various kinds generated using Bart, and discuss their performance.

Integrity constraints, guiding the cleaning of dirty data, are often found to be imprecise as well. Existing studies consider the inaccurate constraints that are oversimplified, and thus refine the constraints via inserting more predicates (attributes). We note that imprecise constraints may not only be oversimplified so that correct data are erroneously identified as violations, but also could be overrefined that the constraints overfit the data and fail to identify true violations. In the latter case, deleting excessive predicates applies. To address the oversimplified and overrefined constraint inaccuracies, in this paper, we propose to repair data by allowing a small variation (with both predicate insertion and deletion) on the constraints. A novel θ-tolerant repair model is introduced, which returns a (minimum) data repair that satisfies at least one variant of the constraints (with constraint variation no greater than θ compared to the given constraints). To efficiently repair data among various constraint variants, we propose a single round, sharing enabled approach. Results on real data sets demonstrate that our proposal can capture more accurate data repairs compared to the existing methods with/without constraint repairs.