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XSPARQL: Traveling between the XML and RDF worlds - and avoiding the XSLT Pilgrimage
A Database Approach to Content-based XML retrieval
This paper describes a rst prototype system for content-based retrieval from XML data. The system's design supports both XPath queries and complex information retrieval queries based on a language modelling approach to information retrieval. Evaluation using the INEX benchmark shows that it is beneficial if the system is biased to retrieve large XML fragments over small fragments
Pattern based processing of XPath queries
As the popularity of areas including document storage and
distributed systems continues to grow, the demand for high
performance XML databases is increasingly evident. This
has led to a number of research eorts aimed at exploiting
the maturity of relational database systems in order to in-
crease XML query performance. In our approach, we use an
index structure based on a metamodel for XML databases
combined with relational database technology to facilitate
fast access to XML document elements. The query process
involves transforming XPath expressions to SQL which can
be executed over our optimised query engine. As there are
many dierent types of XPath queries, varying processing
logic may be applied to boost performance not only to indi-
vidual XPath axes, but across multiple axes simultaneously.
This paper describes a pattern based approach to XPath
query processing, which permits the execution of a group of
XPath location steps in parallel
Fast and Tiny Structural Self-Indexes for XML
XML document markup is highly repetitive and therefore well compressible
using dictionary-based methods such as DAGs or grammars. In the context of
selectivity estimation, grammar-compressed trees were used before as synopsis
for structural XPath queries. Here a fully-fledged index over such grammars is
presented. The index allows to execute arbitrary tree algorithms with a
slow-down that is comparable to the space improvement. More interestingly,
certain algorithms execute much faster over the index (because no decompression
occurs). E.g., for structural XPath count queries, evaluating over the index is
faster than previous XPath implementations, often by two orders of magnitude.
The index also allows to serialize XML results (including texts) faster than
previous systems, by a factor of ca. 2-3. This is due to efficient copy
handling of grammar repetitions, and because materialization is totally
avoided. In order to compare with twig join implementations, we implemented a
materializer which writes out pre-order numbers of result nodes, and show its
competitiveness.Comment: 13 page
Reasoning & Querying – State of the Art
Various query languages for Web and Semantic Web data, both for practical use and as an area of research in the scientific community, have emerged in recent years. At the same time, the broad adoption of the internet where keyword search is used in many applications, e.g. search engines, has familiarized casual users with using keyword queries to retrieve information on the internet. Unlike this easy-to-use querying, traditional query languages require knowledge of the language itself as well as of the data to be queried. Keyword-based query languages for XML and RDF bridge the gap between the two, aiming at enabling simple querying of semi-structured data, which is relevant e.g. in the context of the emerging Semantic Web. This article presents an overview of the field of keyword querying for XML and RDF
Sound ranking algorithms for XML search
Ranking algorithms for XML should reflect the actual combined content and structure constraints of queries, while at the same time producing equal rankings for queries that are semantically equal. Ranking algorithms that produce different rankings for queries that are semantically equal are easily detected by tests on large databases: We call such algorithms not sound. We report the behavior of different approaches to ranking content-and-structure queries on pairs of queries for which we expect equal ranking results from the query semantics. We show that most of these approaches are not sound. Of the remaining approaches, only 3 adhere to the W3C XQuery Full-Text standard
06472 Abstracts Collection - XQuery Implementation Paradigms
From 19.11.2006 to 22.11.2006, the Dagstuhl Seminar 06472 ``XQuery Implementation Paradigms'' was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available
Relational Approach to Logical Query Optimization of XPath
To be able to handle the ever growing volumes of XML documents, effective and efficient data management solutions are needed. Managing XML data in a relational DBMS has great potential. Recently, effective relational storage schemes and index structures have been proposed as well as special-purpose join operators to speed up querying of XML data using XPath/XQuery. In this paper, we address the topic of query plan construction and logical query optimization. The claim of this paper is that standard relational algebra extended with special-purpose join operators suffices for logical query optimization. We focus on the XPath accelerator storage scheme and associated staircase join operators, but the approach can be generalized easily
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