SGML for the Web

XML as a better document technology While HTML was wildly successful, its limitations were becoming more and more clear, even to its creators. XML offered to erase some of the uglier parts of HTML (syntax) and provide a much greater level of flexibility (vocabularies, internationalization).
Fitting in with Web infrastructure XML, like HTML, is text-based, using the element and attribute structures inherited from SGML. XML can re-use pretty much the entire infrastructure built around HTML, with the exception of tools (usually editors and older browsers) built exclusively for the HTML vocabulary.
Reusing HTML's supporting cast XML has been able to take advantage of the specifications built around HTML, including HyperText Transfer Protocol (HTTP), the Document Object Model (DOM), and Cascading Style Sheets (CSS), and has contributed to MathML, Scalable Vector Graphics (SVG), Synchronized Multimedia Integration Language (SMIL), and even the reincarnation of HTML as XML, XHTML.