XML with Incomplete Information: Representation, Querying, and Applications

由于缺乏集中化和对数据质量的控制等因素，Web上的数据--尤其是XML数据--往往是不完整和不一致的。尽管过去十年来，处理XML数据的关系工具的转换和扩展一直是数据管理研究的中心主题，但标准数据库工具箱在处理完整性方面几乎没有提供给我们。事实上，它是关系数据库中最臭名昭著的不发达和最常受到批评的方面之一。此外，除了标准的关系空值之外，XML的灵活性还导致了许多方式来适应数据的不完备性。目前还没有对XML的不完全性进行任何详细的研究。我们的主要目标是进行这样的系统研究，并在Web上的数据管理任务的基础领域开发其应用程序--跨多个独立的应用程序使用数据。我们将研究具有不完全信息的XML的模型和用于查询此类数据的算法技术，特别关注正确性/复杂性的权衡以及算法工具的实用性。我们将研究完整性在涉及XML数据移动的应用程序中的基本作用，例如集成来自不同来源的数据或根据其模式之间的映射在对等点之间移动数据。我们将开发一个规范和算法工具箱，用于处理此类应用中出现的不完全信息。

Data on the Web - particularly XML data - is often incomplete andinconsistent, due to such factors as the lack of centralisation andcontrol over data quality. While the transfer and extension ofrelational tools to deal with XML data has been a central theme indata management research over the past decade, the standard databasetoolbox offers us little in terms of handling ofincompleteness. Indeed, it is one of the most notoriouslyunderdeveloped and most often criticised aspects of relationaldatabases. In addition, the flexibility of XML leads to many ways inwhich incompleteness of data can be accommodated, in addition to thestandard relational null values.There has not yet been any detailed study of incompleteness in XML.Our main goal is to conduct such a systematic study, and develop itsapplications in the area that underlies data management tasks on theWeb -- the use of data across multiple independent applications.We shall investigate models of XML with incomplete information andalgorithmic techniques for querying such data, paying particularattention to the correctness/complexity tradeoffs and to the practicalityof algorithmic tools. We shall investigate the fundamental role ofincompleteness in applications that involve the movement of XML data,such as integration of data from various sources or moving databetween peers according to mappings between their schemas. We shalldevelop a specification and algorithmic toolbox for dealing withincomplete information as it arises in such applications.