|
… XML is so subsetted from SGML that it is only functional as a markup language with effort.
XML is a markup language by DNA but it is not really a syntax good for marking up documents with, meaning the activity of marking up not the result: contrast with HTML which retains tag and delimiter omission a la SGML. Which is
why, for marking up (as an activity), the world uses HTML or wiki. I dont think choice is a bad thing: html, wiki, csv, json when the scenerio clearly suits them and xml otherwise.
This implies that the defining purpose of markup is the activity of marking up. HTML and wiki are instances of rendering engine specific presentation languages
akin to Word or traditional typesetting markup languages. These are minimal uses cases of markup. The greater use case is the application of metadata to content that is divorced from a specific presentation of data allowing for more complex data processing
and/or a greater number of presentations or user agents. This is the promise of SGML and XML. SGML was never intended to have the data with its markup stand alone, but rather to be a component of an SMGL application which consisted of documentation of the
information model plus some plan or implementation for processing the data with its markup defined metadata. People use XML when the benefit of adding metadata to content outweighs the cost of applying that markup. HTML and wiki are used when the primary purpose
of the content presentation of the data to a small handful of user agents, primarily to be viewed by human readers. This why aircraft maintenance manuals are written in XML and not just slapped together in HTML or a wiki. Steve |