XML

Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998 and several other related specifications—all of them free open standards—define XML. XML is an application profile of SGML, Standard Generalized Markup Language (ISO 8879).
==Overview==
The main purpose of XML is serialization, i.e. storing, transmitting, and reconstructing arbitrary data. For two disparate systems to exchange information, they need to agree upon a file format. XML standardizes this process. It is therefore analogous to a lingua franca for representing information.Dykes, Lucinda (2005). XML for Dummies (4th ed.). Hoboken, N.J.: Wiley. ISBN 978-0-7645-8845-7
As a markup language, XML labels, categorizes, and structurally organizes information. XML tags represent the data structure and contain metadata. What's within the tags is data, encoded in the way the XML standard specifies. An additional XML schema (XSD) defines the necessary metadata for interpreting and validating XML. (This is also referred to as the canonical schema.) An XML document that adheres to basic XML rules is "well-formed"; one that adheres to its schema is "valid."
Further guidelines for the use of XML in a networked context appear in RFC 3470, also known as IETF BCP 70, a document covering many aspects of designing and deploying an XML-based language.
==Applications==
XML has come into common use for the interchange of data over the Internet. Hundreds of document formats using XML syntax have been developed,http://xml.coverpages.org/xmlApplications.html including RSS, Atom, Office Open XML, OpenDocument, SVG, COLLADA, and XHTML. XML also provides the base language for communication protocols such as SOAP and XMPP. It is one of the message exchange formats used in the Asynchronous JavaScript and XML (AJAX) programming technique.
==Example==
Here below is the example of the file written in XML of YouTube. It is a sitemap for indexing links to allow search engines to crawl. It can be found here.
 
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
 <sitemap>
 <loc>https://www.youtube.com/ads/sitemap.xml</loc>
 </sitemap>
 ...
 <sitemap>
 <loc>https://news.youtube/sitemap.xml</loc>
 </sitemap>
</sitemapindex>
==See Also==
*XML in Wikipedia.
==References==
Category:Markup languages