Speaking of XML, I saw this recently: Don’t Invent XML Languages by Tim Bray. In addition to pointing to this great list of XML Languages, he introduces “The Big Five” XML Languages and where they should be used.
Suppose you’ve got an application where a markup language would be handy, and you’re wisely resisting the temptation to build your own. What are you going to do, then?
The smartest thing to do would be to find a way to use one of the perfectly good markup languages that have been designed and debugged and have validators and authoring software and parsers and generators and all that other good stuff. Here’s a radical idea: don’t even think of making your own language until you’re sure that you can’t do the job using one of the Big Five: XHTML, DocBook, ODF, UBL, and Atom.