Aren t XML, SGML, and HTML all the same thing?
Not quite. SGML is the `mother tongue’, used for describing thousands of different document types in many fields of human activity, from transcriptions of ancient Irish manuscripts to the technical documentation for stealth bombers, and from patients clinical records to musical notation. ยง HTML is just one of these document types, the one most frequently used in the Web. It defines a simple, fixed type of document with markup designed for a common class of office or technical report, with headings, paragraphs, lists, illustrations, etc, and some provision for hypertext and multimedia. XML is an abbreviated version of SGML, to make it easier for you to define your own document types, and to make it easier for programmers to write programs to handle them. It omits the more complex and less-used parts of SGML in return for the benefits of being easier to write applications for, easier to understand, and more suited to delivery and interoperability over the Web. But it is still SGML, and X
