Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Logical Foundations of Web Data Extraction

  • Christoph Koch
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1155

Definition

Several wrapper programming languages for extracting information from Web pages have been based on logic, specifically on fragments of datalog. This entry shows how logical languages can be used for Web information extraction, and surveys expressiveness and complexity aspects of a foundational logical wrapping language, monadic datalog.

Historical Background

A substantial amount of research has studied the problem of learning wrapper programs from examples (see Wrapper Induction). Unfortunately, it is now known that the expressive power of learnable wrappers is fundamentally limited. This has motivated further work on visual wrapper programming languages, which simplify and speed up wrapper definition. Visual wrapping is now supported by several implemented systems (cf. XWrap [3] and W4F [4]; Lixto [1], a commercial product). The Lixto project was the first to emphasize and study expressiveness of visual wrapper languages. Its approach is based on a datalog-like language,...

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Recommended Reading

  1. 1.
    Baumgartner R, Flesca S, Gottlob G. Visual web information extraction with Lixto. In: Proceedings of the 27th International Conference on Very Large Data Bases; 2001.Google Scholar
  2. 2.
    Gottlob G, Koch C. Monadic datalog and the expressive power of web information extraction languages. J ACM. 2004;51(1):74–113.MathSciNetzbMATHCrossRefGoogle Scholar
  3. 3.
    Liu L, Pu C, Han W. XWRAP: an XML-enabled wrapper construction system for web information sources. In: Proceedings of the 16th IEEE International Conference on Data Engineering; 2000. p. 611–21.Google Scholar
  4. 4.
    Sahuguet A, Azavant F. Building intelligent web applications using lightweight wrappers. Data Knowl Eng. 2001;36(3):283–316.zbMATHCrossRefGoogle Scholar
  5. 5.
    Shen W, Doan A, Naughton JF, Ramakrishnan R. Declarative information extraction using datalog with embedded extraction predicates. In: Proceedings of the 33rd International Conference on Very Large Data Bases; 2007. p. 1033–44.Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Cornell University, IthacaNew YorkUSA
  2. 2.EPFLLausanneSwitzerland

Section editors and affiliations

  • Georg Gottlob
    • 1
  1. 1.Computing Lab.Oxford Univ.OxfordUK