Encyclopedia of Database Systems

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

Wrapper Maintenance

  • Kristina LermanEmail author
  • Craig A. Knoblock
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1158


Wrapper repair; Wrapper verification and reinduction


A Web wrapper is a software application that extracts information from a semi-structured source and converts it to a structured format. While semi-structured sources, such as Web pages, contain no explicitly specified schema, they do have an implicit grammar that can be used to identify relevant information in the document. A wrapper learning system analyzes page layout to generate either grammar-based or “landmark”-based extraction rules that wrappers use to extract data. As a consequence, even slight changes in the page layout can break the wrapper and prevent it from extracting data correctly. Wrapper maintenance is a composite task that (i) verifies that the wrapper continues to extract data correctly from a source, and (ii) repairs the wrapper so that it works on the changed pages.

Historical Background

Wrapper induction algorithms [3, 6, 11] exploit regularities in the page layout to find a set of...

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Copyright information

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

Authors and Affiliations

  1. 1.University of Southern California, Marina del ReyLos AngelesUSA

Section editors and affiliations

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