Information-based distance measures and the canonical reflection of view updates
Information-based distance measures and the canonical reflection of view updates
复制标题
基于信息的距离测量和视图更新的规范反映
DOI：
10.1007/s10472-012-9278-x
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发表时间：
2011
影响因子：
1.2
通讯作者：
S. Hegner
中科院分区：
文献类型：
--
作者：
S. Hegner
对于将数据库视图上的更新反映到主模式的问题，常量补策略正是避免所有更新异常的策略，因此定义了问题的良好解决方案的黄金标准。然而，在这种策略下支持的视图更新的家庭是有限的，因此有时有必要超越它们，尽管是以系统的方式。在这项工作中，这样的扩展策略的调查关系图式。该方法是描述数据库实例的信息内容，然后要求视图更新到主模式的最佳反映体现了最小可能的信息变化。关键属性被确定为视图的强单调性，这意味着视图插入可以总是被反映为对主模式的插入，并且对于删除也是如此。在这种情况下，研究表明，对于插入和删除，存在最佳更新（需要最少的信息变化），并且对于广泛类别的约束来说，在同构之前是唯一的。
For the problem of reflecting an update on a database view to the main schema, the constant-complement strategies are precisely those which avoid all update anomalies, and so define the gold standard for well-behaved solutions to the problem. However, the families of view updates which are supported under such strategies are limited, so it is sometimes necessary to go beyond them, albeit in a systematic fashion. In this work, an investigation of such extended strategies is initiated for relational schemata. The approach is to characterize the information content of a database instance, and then require that the optimal reflection of a view update to the main schema embody the least possible change of information. The key property is identified to be strong monotonicity of the view, meaning that view insertions may always be reflected as insertions to the main schema, and likewise for deletions. In that context it is shown that for insertions and deletions, an optimal update, entailing the least change of information, exists and is unique up to isomorphism for wide classes of constraints.