XML Database Design
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XMI ▶ XML Metadata Interchange
XML M ICHAEL RYS Microsoft Corporation, Sammamish, WA, USA
Synonyms Extensible markup language; XML 1.0
Definition The Extensible Markup Language or XML for short is a markup definition language defined by a World Wide Web Consortium Recommendation that allows annotating textual data with tags to convey additional semantic information. It is extensible by allowing users to define the tags themselves.
Historical Background XML was developed as a simplification of the ISO Standard General Markup Language (SGML) in the mid 1990s under the auspices of the World Wide Web Consortium (W3C). Some of the primary contributors were Jon Bosak of Sun Microsystems (the working group chair), Tim Bray (then working at Textuality and Netscape), Jean Paoli of Microsoft, and C. Michael Sperberg-McQueen of then the University of Chicago. Initially released as a version 1.0 W3C recommendation on 10 Feb. 1998, XML has undergone several revisions since then. The latest XML 1.0 recommendation edition is the fourth edition as of #
2009 Springer ScienceþBusiness Media, LLC
this writing. A fifth edition is currently undergoing review. The fifth edition is adding some functionality into XML 1.0 that was part of the XML 1.1 recommendation, that has achieved very little adoption. Based on the XML recommendation, a whole set of related technologies have been developed, both at the W3C and other places. Some technologies are augmenting the core syntactic XML recommendation such as the XML Namespaces and XML Information Set recommendations, others are building additional infrastructure on it such as the XML Schema recommendation or the XSLT, XPath and XQuery family of recommendations. Since XML itself is being used to define markup vocabularies, it also forms the basis for vertical industry standards in manufacturing, finance and other areas, including standard document formats such as XHTML, DocBook, Open Document Format (ODF) and Office Open XML (OOXML) and forms the foundation of the web services infrastructure.
Foundations XML’s markup format is based on the notion of defining well-formed documents and is geared towards human-readability and international usability (by basing it on Unicode). Among its design goals were ease of implementation by means of a simple specification, especially compared to its predecessor, the SGML specification, and to make it available on a royalty-free basis to both implementers and users. Well-formed documents basically contain markup elements that have a begin tag and an end tag as in the example below: < tag > character data < /tag > Element tags can have attributes associated with it that provide information about the tag, without interfering with the flow of the textual character data that is being marked up:
character data
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XML
Processing instructions can be added to convey processing information to XML processors and comments can be added. And comments can be added for commenting and documentation purposes. = They follow different syntactic forms than element
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