Shihui Zheng

DTD-directed publishing with attribute translation grammars

We present a framework for publishing relational data in XML with respect to a fixed DTD. In data exchange on the Web, XML views of relational data are typically required to conform to a predefined DTD. The presence of recursion in a DTD as well as non-determinism makes it challenging to generate DTD-directed, efficient transformations. Our framework provides a language for defining views that are guaranteed to be DTD-conformant, as well as middleware for evaluating these views. It is based on a novel notion of attribute translation grammars (ATGs). An ATG extends a DTD by associating semantic rules via SQL queries. Directed by the DTD, it extracts data from a relational database, and constructs an XML document. We provide algorithms for efficiently evaluating ATGs, along with methods for statically analyzing them. This yields a systematic and effective approach to publishing data with respect to a predefined DTD.

DVQ: Towards Visual Query Processing of XML Database Systems

XML has been recognized as a promising language for data exchange over the Internet. A number of query languages have been proposed for querying XML data. Most of those languages are path-expression based. One difficulty in forming path-expression based queries is that users have to know the structure of XML data against which the queries were issued. In this paper, we describe a DTD-driven visual query interface for XML database systems. With such an interface, a user can easily form path-expression based queries by clicking elements in the DTD tree displayed on the screen and supplying conditions if necessary. The interface and the query generation process are described in detail.

Enhancing XML Data Processing in Relational System with Indices

Using relational database to query XML documents is becoming a common and viable practice. To meet the request of retrieving XML data on Web, which are usually semi-structured or unstructured, the current database system need to be enhanced with the capabilities of dealing with path expressions and searching for information in text. In this paper, various index mechanisms, which can enhance the query engine of RDBMS with the capabilities of evaluating path expressions and supporting keywords search, are discussed. And some simple experiments are carried out to show the effectiveness of those indices.

What makes the differences: benchmarking XML database implementations

XML is emerging as a major standard for representing data on the World-Wide-Web. Recently, many XML storage models have been proposed to manage XML data. We propose several benchmarks including XMark and XMach in order to assess an XML databases abilities to deal with XML queries. We report our first set of results on benchmarking a set of XML database implementations using two XML benchmarks. In general, XML data can be managed as text files, by existing DBMSs, or by the so-called native XML engines. We implemented three XML database systems. VXMLR, and XParent were built on top of RDBMS, and XBase was implemented as a native XML engine. For each approach, variations on schema mapping and storage methods were also implemented for comparison.

Structural Map: A New Index for Efficient XML Path Expression Processing

XML is merging as the main standard of presentation and exchange on the Internet. Various XML query languages are proposed. As a ubiquitous part of those XML query languages, path expression poses a new challenge for efficient XML query processing in database systems. In this paper, we present a new index structure, Structural Map, for efficient evaluation of path expression queries. Structural Map can be used to support path-indices as well as valueindices in an integrated manner. It is powerful to handle not only simple path expressions but also the branching path expressions and path expressions with predicates efficiently. Performance study shows the Structural Map can improve the performance of XML path expression processing significantly.

DVQ: a DTD-driven Visual Query Interface for XML Database Systems

XML has been recognized as a promising language for data exchange over the Internet. A number of query languages have been proposed for querying XML data. Most of those languages are path-expression based. One difficulty in forming path-expression based queries is that users have to know the structure of XML data against which the queries are issued. In this paper, we describe a DTD-driven visual query interface for XML database systems. With such interface, a user can easily form path-expression based queries by clicking elements in the DTD tree displayed on the screen and supplying conditions if necessary. The interface and the query generation process are described in detail.