Projective distribution of xQuery with updates

Ying Zhang, Nan Tang, Peter Boncz

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

We investigate techniques to automatically decompose any XQuery query-including updating queries specified by the XQuery Update Facility (XQUF)-into subqueries, that can be executed near their data sources, i.e., function-shipping. The main challenge addressed here is to ensure that the decomposed queries properly respect XML node identity and preserve structural properties, when (parts of) XML nodes are sent over the network, effectively copying them. We start by precisely characterizing the conditions, under which pass-by-value parameter passing causes semantic differences between remote execution of an XQuery expression and its local execution. We then formulate a conservative strategy that effectively avoids decomposition in such cases. To broaden the possibilities of query distribution, we extend the pass-by-value semantics to a pass-by-fragment semantics, which keeps better track of node identities and structural properties. The pass-by-fragment semantics is subsequently refined to a pass-by-projection semantics by means of a novel runtime XML projection technique, which safely eliminates most semantic differences between the local and remote execution of an XQuery expression, and strongly reduces message sizes. Finally, we discuss how these techniques can be used for updating queries, both under the standard W3C XQUF specification, as well as under an extended semantics that allows to update remote documents. The proposed techniques are implemented in XRPC, a simple yet efficient XQuery extension that enables function-shipping by adding a Remote Procedure Call mechanism to XQuery. Experiments on MonetDB/XQuery establish the performance potential of our XQuery decomposition techniques.

Original languageEnglish
Article number5453373
Pages (from-to)1059-1076
Number of pages18
JournalIEEE Transactions on Knowledge and Data Engineering
Volume22
Issue number8
DOIs
Publication statusPublished - 6 Jul 2010
Externally publishedYes

Fingerprint

Semantics
XML
Freight transportation
Structural properties
Decomposition
Copying
Specifications
Experiments

Keywords

  • Distributed databases
  • XQuery decomposition

ASJC Scopus subject areas

  • Computational Theory and Mathematics
  • Information Systems
  • Computer Science Applications

Cite this

Projective distribution of xQuery with updates. / Zhang, Ying; Tang, Nan; Boncz, Peter.

In: IEEE Transactions on Knowledge and Data Engineering, Vol. 22, No. 8, 5453373, 06.07.2010, p. 1059-1076.

Research output: Contribution to journalArticle

Zhang, Ying ; Tang, Nan ; Boncz, Peter. / Projective distribution of xQuery with updates. In: IEEE Transactions on Knowledge and Data Engineering. 2010 ; Vol. 22, No. 8. pp. 1059-1076.
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