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261
Staircase Join: Teach a Relational DBMS to Watch its (Axis) Steps
- IN PROC. OF THE 29TH INT’L CONFERENCE ON VERY LARGE DATABASES (VLDB
, 2003
"... Relational query processors derive much of their effectiveness from the awareness of specific table properties like sort order, size, or absence of duplicate tuples. This text applies (and adapts) this successful principle to database-supported XML and XPath processing: the relational system is made ..."
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Cited by 105 (24 self)
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Relational query processors derive much of their effectiveness from the awareness of specific table properties like sort order, size, or absence of duplicate tuples. This text applies (and adapts) this successful principle to database-supported XML and XPath processing: the relational system is made tree aware, i.e., tree properties like subtree size, intersection of paths, inclusion or disjointness of subtrees are made explicit. We propose a local change to the database kernel, the staircase join, which encapsulates the necessary tree knowledge needed to improve XPath performance. Staircase join
XQuery on SQL Hosts
- In VLDB Conf
, 2004
"... Relational database systems may be turned into efficient XML and XPath processors if the system is provided with a suitable relational tree encoding. This paper extends this relational XML processing stack and shows that an RDBMS can also serve as a highly efficient XQuery runtime environment. Our a ..."
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Cited by 81 (31 self)
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Relational database systems may be turned into efficient XML and XPath processors if the system is provided with a suitable relational tree encoding. This paper extends this relational XML processing stack and shows that an RDBMS can also serve as a highly efficient XQuery runtime environment. Our approach is purely relational: XQuery expressions are compiled into SQL code which operates on the tree encoding. The core of the compilation procedure trades XQuery’s notions of variable scopes and nested iteration (FLWOR blocks) for equi-joins. The resulting relational XQuery processor closely adheres to the language semantics, e.g., it respects node identity as well as document and sequence order, and can support XQuery’s full axis feature. The system exhibits quite promising performance figures in experiments. Somewhat unexpectedly, we will also see that the XQuery compiler can make good use of SQL’s OLAP functionality. 1
eXist: An Open Source Native XML Database
- Web-Services, and Database Systems, NODe 2002 Web and Database-Related Workshops
, 2002
"... Abstract. With the advent of native and XML enabled database systems, techniques for efficiently storing, indexing and querying large collections of XML documents have become an important research topic. This paper presents the storage, indexing and query processing architecture of eXist, an Open So ..."
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Cited by 81 (0 self)
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Abstract. With the advent of native and XML enabled database systems, techniques for efficiently storing, indexing and querying large collections of XML documents have become an important research topic. This paper presents the storage, indexing and query processing architecture of eXist, an Open Source native XML database system. eXist is tightly integrated with existing tools and covers most of the native XML database features. An enhanced indexing scheme at the architecture’s core supports quick identification of structural node relationships. Based on this scheme, we extend the application of path join algorithms to implement most parts of the XPath query language specification and add support for keyword search on element and attribute contents. 1. Overview eXist
An Efficient and Versatile Query Engine for TopX Search
- In VLDB
, 2005
"... This paper presents a novel engine, coined TopX, for efficient ranked retrieval of XML documents over semistructured but nonschematic data collections. The algorithm follows the paradigm of threshold algorithms for top-k query processing with a focus on inexpensive sequential accesses to index lists ..."
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Cited by 80 (21 self)
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This paper presents a novel engine, coined TopX, for efficient ranked retrieval of XML documents over semistructured but nonschematic data collections. The algorithm follows the paradigm of threshold algorithms for top-k query processing with a focus on inexpensive sequential accesses to index lists and only a few judiciously scheduled random accesses. The difficulties in applying...
Efficient Structural Joins on Indexed XML Documents
- In VLDB
, 2002
"... Queries on XML documents typically combine selections on element contents, and, via path expressions, the structural relationships between tagged elements. Structural joins are used to find all pairs of elements satisfying the primitive structural relationships specified in the query, namely, ..."
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Cited by 79 (3 self)
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Queries on XML documents typically combine selections on element contents, and, via path expressions, the structural relationships between tagged elements. Structural joins are used to find all pairs of elements satisfying the primitive structural relationships specified in the query, namely, parent child and ancestor descendant relationships. Efficient support for structural joins is thus the key to efficient implementations of XML queries. Recently proposed node numbering schemes enable the capturing of the XML document structure us- ing traditional indices (such as B+-trees or R-trees). This paper proposes efficient struc- tural join algorithms in the presence of tag indices. We first concentrate on using B+- trees and show how to expedite a structural join by avoiding collections of elements that do not participate in the join. We then intro- duce an enhancement (based on sibling pointers) that further improves performance. Such sibling pointers are easily implemented and dynamically maintainable. We also present a structural join algorithm that utilizes R-trees.
Holistic Twig Joins on Indexed XML Documents
- In Proc. of VLDB
, 2003
"... Finding all the occurrences of a twig pattern specified by a selection predicate on multiple elements in an XML document is a core operation for e#cient evaluation of XML queries. Holistic twig join algorithms were proposed recently as an optimal solution when the twig pattern only involves an ..."
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Cited by 75 (5 self)
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Finding all the occurrences of a twig pattern specified by a selection predicate on multiple elements in an XML document is a core operation for e#cient evaluation of XML queries. Holistic twig join algorithms were proposed recently as an optimal solution when the twig pattern only involves ancestordescendant relationships. In this paper, we address the problem of e#cient processing of holistic twig joins on all/partly indexed XML documents. In particular, we propose an algorithm that utilizes available indices on element sets. While it can be shown analytically that the proposed algorithm is as e#cient as the existing state-of-the-art algorithms in terms of worst case I/O and CPU cost, experimental results on various datasets indicate that the proposed index-based algorithm performs significantly better than the existing ones, especially when binary structural joins in the twig pattern have varying join selectivities.
Accelerating Xpath Evaluation in Any RDBMS.
- ACM Transactions on Database Systems,
, 2005
"... ..."
XR-Tree: Indexing XML data for efficient structural join. ICDE
, 2003
"... XML documents are typically queried with a combination of value search and structure search. While querying by values can leverage traditional database technologies, evaluating structural relationship, specifically parent-child or ancestor-descendant relationship, between XML element sets has impose ..."
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Cited by 70 (7 self)
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XML documents are typically queried with a combination of value search and structure search. While querying by values can leverage traditional database technologies, evaluating structural relationship, specifically parent-child or ancestor-descendant relationship, between XML element sets has imposed a great challenge on efficient XML query processing. This paper proposes XR-tree, namely, XML Region Tree, which is a dynamic external memory index structure specially designed for strictly nested XML data. The unique feature of XR-tree is that, for a given element, all its ancestors (or descendants) in an element set indexed by an XRtree can be identified with optimal worst case I/O cost. We then propose a new structural join algorithm that can evaluate the structural relationship between two XR-tree indexed element sets by effectively skipping ancestors and descendants that do not participate in the join. Our extensive performance study shows that the XR-tree based join algorithm significantly outperforms previous algorithms. 1.
HOPI: An efficient connection index for complex XML document collections
- In 9th Int. Conference on Extending Database Technology (EDBT
, 2004
"... Abstract. In this paper we present HOPI, a new connection index for XML documents based on the concept of the 2–hop cover of a directed graph introduced by Cohen et al. In contrast to most of the prior work on XML indexing we consider not only paths with child or parent relationships between the nod ..."
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Cited by 64 (5 self)
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Abstract. In this paper we present HOPI, a new connection index for XML documents based on the concept of the 2–hop cover of a directed graph introduced by Cohen et al. In contrast to most of the prior work on XML indexing we consider not only paths with child or parent relationships between the nodes, but also provide space – and time–efficient reachability tests along the ancestor, descendant, and link axes to support path expressions with wildcards in our XXL search engine. We improve the theoretical concept of a 2–hop cover by developing scalable methods for index creation on very large XML data collections with long paths and extensive cross–linkage. Our experiments show substantial savings in the query performance of the HOPI index over previously proposed index structures in combination with low space requirements.
XPRESS: a queriable compression for XML data
- In Proceedings of the 2003 ACM SIGMOD International Conference on Management of Data
, 2003
"... Like HTML, many XML documents are resident on native file systems. Since XML data is irregular and verbose, the disk space and the network bandwidth are wasted. To overcome the verbosity problem, the research on compressors for XML data has been conducted. However, some XML compressors do not suppor ..."
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Cited by 61 (6 self)
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Like HTML, many XML documents are resident on native file systems. Since XML data is irregular and verbose, the disk space and the network bandwidth are wasted. To overcome the verbosity problem, the research on compressors for XML data has been conducted. However, some XML compressors do not support querying compressed data, while other XML compressors which support querying compressed data blindly encode tags and data values using predefined encoding methods. Thus, the query performance on compressed XML data is degraded. In this paper, we propose XPRESS, an XML compressor which supports direct and efficient evaluations of queries on compressed XML data. XPRESS adopts a novel encoding method, called reverse arithmetic encoding, which is intended for encoding label paths of XML data, and applies diverse encoding methods depending on the types of data values. Experimental results with real-life data sets show that XPRESS achieves significant improvements on query performance for compressed XML data and reasonable compression ratios. On the average, the query performance of XPRESS is 2.83 times better than that of an existing XML compressor and the compression ratio of XPRESS is 73%. 1.
