[SGML] was an extremely comprehensive standard for which hardly a single fully compliant parser was ever written. Many of its features, even implemented ones, are hardly used. On the other hand, it lacks various useful features. [XML] was designed to address these shortcomings while reducing the language specification to a small set of rules in order to be easily and consistently parsable. It lacks features such as [CONCUR] but adds others such as [NameSpace]s (as good an idea in a MarkupLanguage as they are in a ProgrammingLanguage). 

  

 [XML] is specialised using a [DTD] or a [Schema] to describe the structure of data within a [XML] document. Each specialisation is actually a new language for marking up a particular type of data. Thus DocBook is a specialisation for marking up the text of books, [XHTML] is a specialisation for marking up web pages, [MathML] is a specialisation for marking up mathematical equations, tables and formulae and [XSLT] is a specialisation for marking up a programming language (a FunctionalLanguage written in XML). 

 ** Microsoft's secret weapon against [Sun]'s Open Office 

 ** Sun's secret weapon against [Microsoft]'s Office 

 ** The town bicycle 

 ;: %%% --Rick Jelliffe