XML (eXtensible Markup Language) is a simplified subset of SGML (Standard Generalized Markup Language). It is developed and maintained under the lead-management of the W3C and aims at the description of classes of documents with respect to their distribution on the internet. An XML-description differentiates between structure, information and representation of the documents.
XML Schemas express shared vocabularies and allow machines to carry out rules made by people. They provide a means for defining the structure, content and semantics of XML documents.
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