摘要:由于数据缺失，数据库用户通常无法获得查询结果中的预期答案.它被称为"Why-not问题"，即"为什么预期的元组不会出现在结果中".现有的方法通过列举可能的元组值来解释Why-not问题.枚举所给出解释的数量往往太大，无法由用户探索.完整性约束，如函数依赖，被用来排除不合格的解释.然而，许多属性在简化后解释中仅仅表示为变量，用户可能仍然无法理解.由于数据稀疏性，许多不合理的解释也会被推荐给用户.提出通过研究元组间两两比较关系，从而对Why-not问题的解释进行排序的方法.首先，重新定义为什么Why-not问题解释的形式没有变量，以便于用户理解；其次，对元组中的相等/不相等关系进行表示，提出在{0，1}表示的元组对的基础上学习统计模型，从而解决直接在原始数据上学习所带来的稀疏性问题，许多模型可以被用来推断概率，包括统计分布、分类和回归；最后，根据推断的概率对解释进行评价和排序.实验结果证明：利用统计、分类和回归方法计算两两关系概率分布的方法，可以为用户寻找Why-not问题的解释并返回较为高质量的解释.



Abstract:Database users often fails to obtain the expected answer in the query results, since databases are often incomplete with missing data. It is known as the Why-not problem, that is, "why the expected tuples do not appear in the results". Existing methods present the explanations of the Why-not problem by enumerating possible values. The number of explanations presented by enumeration is often too large to explore by users. Integrity constraints, such as function dependencies, are employed to rule out irrational explanations. Unfortunately, many attributes are simply represented as variables in the reduced explanations, which the users may still not understand. There are also many unreasonable explanations, owing to data sparsity. This work proposes to study the pair-wise relationships of tuples as the features for ranking Why-not explanations. First, the format of Why-not problem explanations is re-defined, without variables, for easy understanding by users. Secondly, the equality/inequality relationships in tuple pairs are represented. Instead of learning over the original data with sparsity issue, to learn statistical models over the {0,1} representation of tuple pairs is proposed. A number of models are employed to infer the probability, including statistical distribution, classification, and regression. Finally, the explanations are evaluated and ranked according to the inferred probability. Experiments shows that high-quality explanations for Why-not question can be returned using pair-wise method.



PDF全文下载地址:

http://jos.org.cn/jos/article/pdf/5700