固定不动点和主动完整性约束
Grounded Fixpoints and Active Integrity Constraints
摘要：
主动完整性约束的形式主义被引入作为一种方式来指定特定类别的完整性约束的关系数据库连同偏好如何修复现有的不一致。这种完整性约束的基于规则的语法还提供了用于找到实现最佳渐近复杂度的这种修复的算法。然而，为这些完整性约束提出的不同语义都表现出一些反直觉的例子。在这项工作中，我们期待在积极的完整性约束，使用代数不动点理论的想法。我们展示了如何数据库修复可以建模为特定的运营商对数据库的不动点，并研究如何接地不动点的概念引起相应的概念接地数据库修复，捕捉几个自然的直觉，特别是避免了以前的替代语义问题。为了研究接地修复在其充分的普遍性，我们需要推广的概念接地不动点的非确定性运营商。我们提出了这样一个定义，并说明其在数据库上下文中的可扩展性。
英文摘要：
The formalism of active integrity constraints was introduced as a way to specify particular classes of integrity constraints over relational databases together with preferences on how to repair existing inconsistencies. The rule-based syntax of such integrity constraints also provides algorithms for finding such repairs that achieve the best asymptotic complexity. However, the different semantics that have been proposed for these integrity constraints all exhibit some counter-intuitive examples. In this work, we look at active integrity constraints using ideas from algebraic fixpoint theory. We show how database repairs can be modeled as fixpoints of particular operators on databases, and study how the notion of grounded fixpoint induces a corresponding notion of grounded database repair that captures several natural intuitions, and in particular avoids the problems of previous alternative semantics. In order to study grounded repairs in their full generality, we need to generalize the notion of grounded fixpoint to non-deterministic operators. We propose such a definition and illustrate its plausibility in the database context.
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