Temporal slicing in the evaluation of XML queries

Dengfeng Gao, Richard T. Snodgrass

Research output: Chapter in Book/Report/Conference proceedingConference contribution

59 Scopus citations


As with relational data, XML data changes over time with the creation, modification, and deletion of XML documents. Expressing queries on timevarying (relational or XML) data is more difficult than writing queries on nontemporal data. In this paper, we present a temporal XML query language, XQuery, in which we add valid time support to XQuery by minimally extending the syntax and semantics of XQuery. We adopt a stratum approach which maps a XQuery query to a conventional XQuery. The paper focuses on how to perform this mapping, in particular, on mapping sequenced queries, which are by far the most challenging. The critical issue of supporting sequenced queries (in any query language) is time-slicing the input data while retaining period timestamping. Timestamps are distributed throughout an XML document, rather than uniformly in tuples, complicating the temporal slicing while also providing opportunities for optimization. We propose four optimizations of our initial maximally-fragmented time-slicing approach: selected node slicing, copy-based perexpression slicing, in-place per-expression slicing, and idiomatic slicing, each of which reduces the number of constant periods over which the query is evaluated. While performance tradeoffs clearly depend on the underlying XQuery engine, we argue that there are queries that favor each of the five approaches.

Original languageEnglish (US)
Title of host publicationProceedings - 29th International Conference on Very Large Data Bases, VLDB 2003
EditorsJohann Christoph Freytag, Peter C. Lockemann, Serge Abiteboul, Michael J. Carey, Patricia G. Selinger, Andreas Heuer
PublisherMorgan Kaufmann
Number of pages12
ISBN (Electronic)0127224424, 9780127224428
StatePublished - 2003
Event29th International Conference on Very Large Data Bases, VLDB 2003 - Berlin, Germany
Duration: Sep 9 2003Sep 12 2003

Publication series

NameProceedings - 29th International Conference on Very Large Data Bases, VLDB 2003


Other29th International Conference on Very Large Data Bases, VLDB 2003

ASJC Scopus subject areas

  • Software
  • Information Systems
  • Hardware and Architecture
  • Information Systems and Management
  • Computer Science Applications
  • Computer Networks and Communications


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