XML (eXtensible Markup Language) is a W3C for generating markup ​​for special needs.

It is one of the subtypes of SGML (acronym for Standard Generalized Markup Language) capable of describing various types of data .

Its main purpose is to facilitate the sharing of information over the internet. Languages ​​based on XML include XHTML (format for web ), RDF , SDMX, SMIL, MathML (format for mathematical expressions), NCL, XBRL, XSIL, and SVG (vector graphics format).

The main feature of XML, which creates a single infrastructure for various languages, is that unknown and little-used languages ​​can also be defined without much work and without the need to be submitted to standardization committees.