Wang Chiew Tan

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With the proliferation of database views and curated databases, the issue of data provenance { where a piece of data came from and the process by which it arrived in the database { is becoming increasingly important, especially in scienti c databases where understanding provenance is crucial to the accuracy and currency of data. In this paper we describe an(More)
A schema mapping is a specification that describes how data structured under one schema (the source schema) is to be transformed into data structured under a different schema (the target schema). Schema mappings play a key role in numerous areas of database systems, including database design, information integration, and model management. A fundamental(More)
We present an annotation management system for relational databases. In this system, every piece of data in a relation is assumed to have zero or more annotations associated with it and annotations are propagated along, from the source to the output, as data is being transformed through a query. Such an annotation management system could be used for(More)
A fundamental problem in information integration is to precisely specify the relationships, called mappings, between schemas. Designing mappings is a time-consuming process. To alleviate this problem, many mapping systems have been developed to assist the design of mappings. However, a benchmark for comparing and evaluating these systems has not yet been(More)
We study absolute and relative keys for XML, and investigate their associated decision problems. We argue that these keys are important to many forms of hierarchically structured data including XML documents. In contrast to other proposals of keys for XML, these keys can be reasoned about efficiently. We show that the (finite) satisfiability problem for(More)
Different notions of provenance for database queries have been proposed and studied in the past few years. In this article, we detail three main notions of database provenance, some of their applications, and compare and contrast amongst them. Specifically, we review why, how, and where provenance, describe the relationships among these notions of(More)
We study two classes of view update problems in relational databases. We are given a source database <i>S</i>, a monotone query <i>Q</i>, and the view <i>Q</i>(<i>S</i>) generated by the query. The first problem that we consider is the classical view deletion problem where we wish to identify a minimal set <i>T</i> of tuples in <i>S</i> whose deletion will(More)
Archiving is important for scientific data, where it is necessary to record all past versions of a database in order to verify findings based upon a specific version. Much scientific data is held in a hierachical format and has a key structure that provides a canonical identification for each element of the hierarchy. In this article, we exploit these(More)