Closed world data exchange
Closed world data exchange
复制标题
封闭世界数据交换
DOI：
10.1145/1966385.1966392
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Nicole Schweikardt
中科院分区：
文献类型：
--
作者：
André Hernich;L. Libkin;Nicole Schweikardt
数据交换处理将以某种源格式结构化的数据转换为以某种目标格式结构化的数据，给定源和目标之间关系的规范以及可能对目标的约束;并以与源中的信息语义一致的方式回答对目标的查询。最近对数据交换的理论基础进行了积极的探讨。人们还注意到，数据交换中的查询回答的标准语义可能会导致违反直觉或异常的答案。
在本文中，我们解释说，这种行为是由于解决方案可以包含虚构的信息（与源实例无关的信息），并且目标实例中不完整信息的存在被忽略了。特别是，适当的查询评估技术的数据库与空值没有被使用，并没有封闭和开放世界语义之间的区别。
我们提出了一个概念的解决方案，称为CWA解决方案，这是基于封闭世界的假设。对于没有目标约束的数据交换设置，CWA解空间有两个极值点：规范泛解（最大CWA解）和泛解的核（最小CWA解），这两个极值点在数据交换中得到了很好的研究.在目标存在约束的情况下，泛解的核心仍然是最小CWA解，但可能不存在唯一的最大CWA解。我们将展示如何定义的语义查询回答考虑到不完整的信息，并显示一些著名的异常消失的新的语义。本文还包含查询回答的复杂性，查询的上近似值（maybe-answers）和各种扩展的结果。
Data exchange deals with translating data structured in some source format into data structured in some target format, given a specification of the relationship between the source and the target and possibly constraints on the target; and answering queries over the target in a way that is semantically consistent with the information in the source. Theoretical foundations of data exchange have been actively explored recently. It was also noticed that the standard semantics for query answering in data exchange may lead to counterintuitive or anomalous answers.
In the present article, we explain that this behavior is due to the fact that solutions can contain invented information (information that is not related to the source instance), and that the presence of incomplete information in target instances has been ignored. In particular, proper query evaluation techniques for databases with nulls have not been used, and the distinction between closed and open world semantics has not been made.
We present a concept of solutions, called CWA-solutions, that is based on the closed world assumption. For data exchange settings without constraints on the target, the space of CWA-solutions has two extreme points: the canonical universal solution (the maximal CWA-solution) and the core of the universal solutions (the minimal CWA-solution), both of them well studied in data exchange. In the presence of constraints on the target, the core of the universal solutions is still the minimal CWA-solution, but there may be no unique maximal CWA-solution. We show how to define the semantics of query-answering taking into account incomplete information, and show that some of the well-known anomalies go away with the new semantics. The article also contains results on the complexity of query-answering, upper approximations to queries (maybe-answers), and various extensions.
逻辑和数据交换：哪些解决方案是“好的”解决方案？
DOI：
10.1007/978-3-642-15164-4_4
发表时间：
2008
期刊：
影响因子：
--
作者：
André Hernich;Nicole Schweikardt
通讯作者：
Nicole Schweikardt
关系和 XML 数据交换
DOI：
10.2200/s00297ed1v01y201008dtm008
发表时间：
2010
期刊：
Synthesis Lectures on Data Management
影响因子：
--
作者：
Arenas M
通讯作者：
Arenas M