ZML is a text format that combines Wiki-style formatting with an alternative syntax for XML inspired by SLiP. Like the Wiki and SLiP formats its goal is to be a human-friendly markup language: simple, clear, and concise.
This combination enables you to author XML and HTML documents with (nearly) the same ease as a wiki entry.
For more info see:
You can play with ZML in the ZML Sandbox or download the ZML command-line tool here (requires Python).