XML is a simplification (proper subset) of SGML designed to eventually replace HTML serialization (as XHTML + SVG etc.), but that never happened. For a detaile

XML is a simplification (proper subset) of SGML designed to eventually replace HTML serialization (as XHTML + SVG etc.), but that never happened. For a detailed discussion about the (mostly trivial) features of modern HTML not in SGML see [1]. Edit: > HTML [...] was itself an application of SGML (before, you know, it wasn't anymore) You're right, "not an application of SGML" is the phrase the HTML spec itself uses to describe its relationship with SGML, but I think that doesn't make HTML any less of an SGML application; it's kindof like saying American is not an application of English. [1]: http://sgmljs.net/blog/blog1701.html http://sgmljs.net/blog/blog1701.html