Encyclopedia of Database Systems

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

XML Types

  • Frank NevenEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1563


XML schemas


To constrain the structure of allowed XML documents, for instance with respect to a specific application, a target schema can be defined in some schema language. A schema consists of a sequence of type definitions specifying a (possibly infinite) class of XML documents. A type can be assigned to every element in a document valid w.r.t. a schema. As the same holds for the root element, the document itself can also be viewed to be of a specific type. The schema languages DTDs, XML Schema, and Relax NG, are, on an abstract level, different instantiations of the abstract model of unranked regular tree languages.

Historical Background

Brüggemann-Klein et al. [3] were the first to revive the theory of regular unranked tree automata [14] for the modelling of XML schema languages. Murata et al. [10] provided the formal taxonomy as presented here. Martens et al. [8] characterized the expressiveness of the different models and provided type-free abstractions.


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Copyright information

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

Authors and Affiliations

  1. 1.Hasselt University and Transnational University of LimburgDiepenbeekBelgium

Section editors and affiliations

  • Sihem Amer-Yahia
    • 1
  1. 1.Laboratoire d'Informatique de GrenobleCNRS and LIGGrenobleFrance