XML Schema

What Does XML Schema Mean?

An XML schema is the structural layout of an XML document, expressed in terms of constraints and contents of the document. Constraints are expressed using a combination of the following:

  • Grammatical rules governing the order of elements
  • Data types governing an element and content attribute
  • Boolean predicates that the content has to satisfy
  • Specialized rules including uniqueness and referential integrity constraints

Techopedia Explains XML Schema

XML schemas are expressed using Document Type Definition (DTD) language, which is native to the XML specification but with a fairly limited capability. An XML document can be associated with a schema language, either by markup in the XML document or through some external means.

The process of checking whether an XML document adheres to a schema is called validation. XML documents are valid if they satisfy schema requirements with which they are associated, including constraints such as:

  • Structure as specified by a regular expression syntax
  • Requirements for interpretation of character data
  • Elements and attributes to be included along with their allowed structure

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Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.