I was wondering what "profile" means in Wikipedia:
XML is a profile of an ISO standard SGML, and most of XML comes from SGML unchanged.
HTML is a subset of SGML.
XML is a highly functional subset of SGML.
XHTML extends and subsets HTML.
Does "one being a subset of another" mean that code in the first is also syntactically correct and semantically the same as in the second?
As in the sense of elementary set theory,
- are HTML, XML and XHTML all different subsets of SGML?
- do XML and HTML almost not intersect each other?
- is XHTML a superset of both XML and HTML?
- Can I expect some more concise and clear summation of the differences in the purposes of the four and/or when to use which, than the link above? I am really confused about the clear line between their intended purposes.
XML is not a single Markup Language. It is a metalanguage to let users design their own markup language.
I was wondering how to understand XML and HTML are both subsets of SGML, but HTML is a markup language while XML is not a markup language but a metalanguage for designing markup languages?
Are SGML and XHTML both also metalanguage for designing markup language?
- As in both links mention that HTML is an applicaiton of SGML as well as a subset of SGML, and XHTML is an application of XML. I wonder what differences are between saying one language is an application of another, and one language is a subset of another?
Thanks and regards!