Earlier quoted context omitted.
The funny thing about XML is that it was explicitly conceived to solve problems of representing, translating and transmitting component models and configuration. The sad thing is that it was abused, horribly, in the early naughts when people tried to take it too far. On the one hand it was rushed out without the proper tooling and you had humans typing raw xml without the right amount of support from intelligent auto…
> XML still survives, though. The tooling is good. If you type XAML or HTML in the right editors, it's serves the purpose competently and without drama. HTML isn't XML, though XML was inspired by HTML and HTML has an XML serialization. IIRC, some or all of the versions of XAML aren't, strictly, XML either, merely XML-derivedl0
No. HTML used to be "an application" of SGML. Meaning HTML brings a profile for SGML features (formerly, an SGML declaration determining things such as allowing tag inference and other minimization) plus a DTD grammar. Though HTML has also quirks for script/style elements, and URLs.
OTOH, XML, like SGML, is a markup meta-language and a proper subset of SGML (also with a fixed SGML declaration disallowing tag inference and almost all other minimization features). XML was introduced by W3C (the SGML "extended review board") as the markup meta-language for new vocabularies on the web going forward around 1997 to eventually replace HTML. While that hasn't happened, SVG and MathML have been specified using XML.
Details on (my pages) below.
[1]: http://sgmljs.net/blog/blog1701.html (the "TALK" slides)