An Inflationary Fixed Point Operator in XQuery

Afanasiev, Loredana; Grust, Torsten; Marx, Maarten; Rittinger, Jan; Teubner, Jens

doi:10.1109/icde.2008.4497604

Cited by 6 publications

(9 citation statements)

References 21 publications

(24 reference statements)

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“…4We tested several xpath queries with different dtds, which are subgraphs of the real-life dtds BI-OML using the same database. The main difference between (1) and 4is that the former tested the same queries with different databases, and the latter tested different queries with the same database. (5) Finally, we examined the numbers of operators (lfp, etc) in the sql queries generated by CycleE and CycleE X , respectively.…”

Section: A Performance Studymentioning

confidence: 99%

“…3, the notion of extended xpath expressions yields a low polynomial-time performance guarantee on query translation from xpath to sql; in contrast, direct use of xpath or regular xpath [48] in the translation may incur exponential blowup. Furthermore, this notion is also useful in developing native xml query engines [1,19]. 2As opposed to prior work [11,39,62], our approach leads to a lightweight tool that provides a variety of commercial rdbms with an immediate capability to answer xpath queries over recursive dtds, requiring only low-end rdbms features instead of the advanced sql'99 recursion functionality.…”

Section: Introductionmentioning

confidence: 99%

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Query translation from XPath to SQL in the presence of recursive DTDs

Fan

et al. 2009

The VLDB Journal

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We study the problem of evaluating xpath queries over xml data that is stored in an rdbms via schema-based shredding. The interaction between recursion (descendantsaxis) in xpath queries and recursion in dtds makes it challenging to answer xpath queries using rdbms. We present a new approach to translating xpath queries into sql queries based on a notion of extended XPath expressions and a simple least fixpoint (lfp) operator. Extended xpath expressions are a mild extension of xpath, and the lfp operator takes a single input relation and is already supported by most commercial rdbms. We show that extended xpath expressions are capable of capturing both dtd recursion and xpath queries in a uniform framework. Furthermore, they can be translated into an equivalent sequence of sql queries with the lfp operator. We present algorithms for rewriting xpath queries over An extended abstract was presented at the 31st international conference on Very Large Data Bases (VLDB), 2005.

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Section: A Performance Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Query translation from XPath to SQL in the presence of recursive DTDs

Fan

et al. 2009

The VLDB Journal

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“…A consequence is that "new" encodings can be obtained by using subsets of the four properties to store the structural part of the XML tree. 2 One such encoding is illustrated in Fig. 1 …”

Section: Pre/post-based Tree Encodingsmentioning

confidence: 99%

“…An extension recently built into Pathfinder [2] aims to explore one particular flavor of recursion, the support for transitive closure. Its evaluation has been studied extensively in the context of deductive databases, and any decent SQL processor readily ships with support for transitive closure.…”

Section: Hitting the Limitsmentioning

confidence: 99%

The relational XQuery puzzle: a look-back on the pieces found so far

Teubner

2009

Comp. Sci. Res. Dev.

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Given the tremendous versatility of relational database implementations toward a wide range of database problems, it seems only natural to consider them as backends for XML data processing. Yet, the assumptions behind the language XQuery are considerably different to those in traditional RDBMSs. The underlying data model is a tree, data and results carry an intrinsic order, queries are described using explicit iteration and, after all, problems are everything else but regular.Solving the relational XQuery puzzle, therefore, has challenged a number of research groups over the past years. The purpose of this article is to summarize and assess some of the results that have been obtained during this period to solve the puzzle. Our main focus is on the Pathfinder XQuery compiler, a full reference implementation of a purely relational XQuery processor. As we dissect its components, we relate them to other work in the field and also point to open problems and limitations in the context of relational XQuery processing. selbstverständlich, diese Systeme auch als Back-Ends für die Verarbeitung von XML einzusetzen. Jedoch unterscheiden sich die Annahmen hinter der Anfragesprache XQuery sehr deutlich von denen in strikt relationalen Systemen. Das zugrundeliegende Datenmodell ist der Baum, Daten und Ergebnisse sind inhärent geordnet, Anfragen werden formuliert mit Hilfe expliziter Iteration und die zu behandelnden Probleme sind alles andere als regulär.Der Lösung dieses relationalen XQuery-Puzzles haben sich in den vergangenen Jahren zahlreiche Forschergruppen angenommen. Ziel dieses Artikels ist es, einige der Ergebnisse daraus zusammenzufassen und zu evaluieren. Unser Schwerpunkt wird der XQuery-Compiler Pathfinder sein, eine vollständige Referenzimplementation eines strikt relationalen XQuery-Prozessors. Während wir einzelne Komponenten von Pathfinder zerlegen, stellen wir sie in Bezug zuähnlichen Arbeiten, zeigen dabei aber auch offene Probleme und Einschränkungen im Bereich relationaler XQuery-Verarbeitung auf.

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“…Such functions which access collections require an evaluation model that supports fixed point computations. The technique required to implement recursive queries is essentially the same used in recursive SQL, and one approach for XQuery was proposed in [1]. Our current prototype does not implement the technique.…”

Section: Limitationsmentioning

confidence: 99%

Versatile XQuery Processing in MapReduce

Sauer

Bächle

Härder

2013

Advances in Databases and Information Systems

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Abstract. The MapReduce (MR) framework has become a standard tool for performing large batch computations-usually of aggregative nature-in parallel over a cluster of commodity machines. A significant share of typical MR jobs involves standard database-style queries, where it becomes cumbersome to specify map and reduce functions from scratch. To overcome this burden, higher-level languages such as HiveQL, PigLatin, and JAQL have been proposed to allow the automatic generation of MR jobs from declarative queries. We identify two major problems of these existing solutions: (i) they introduce new query languages and implement systems from scratch for the sole purpose of expressing MR jobs; and (ii) despite solving some of the major limitations of SQL, they still lack the flexibility required by big data applications. We propose BrackitMR, an approach based on the XQuery language with extended JSON support. XQuery not only is an established query language, but also has a more expressive data model and more powerful language constructs, enabling a much greater degree of flexibility. From a system design perspective, we extend an existing single-node query processor, Brackit, adding MR as a distributed coordination layer. Such heavy reuse of the standard query processor not only provides performance, but also allows for a more elegant design which transparently integrates MR processing into a generic query engine.

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An Inflationary Fixed Point Operator in XQuery

Abstract: Abstract

Cited by 6 publications

References 21 publications

Query translation from XPath to SQL in the presence of recursive DTDs

Query translation from XPath to SQL in the presence of recursive DTDs

The relational XQuery puzzle: a look-back on the pieces found so far

Versatile XQuery Processing in MapReduce

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