What alternative syntaxes are there for expressing XML?

Question

What human-readable and human-editable syntaxes exist that can be automatically converted to and from XML with no loss of expressivity. In other words, an updated version of this list. The three syntaxes mentioned there are:

• SOX
• PYX
• SLiP

Are there others? (This isn't about alternatives to XML, like JSON, but simply easier ways for humans to maintain XML files using a text editor).

Answer 1

Some more answers:

• CompactXML - one alternative general purpose XML syntax, looks fairly sensible
• SLAX - an alternative syntax for XSL. Looks like an odd hybrid of JavaScript, CSS, and...I'm not sure.
• RELAX NG - a schema language for XML (like XSL), with a compact alternative syntax.

And some useful links:

• XSugar - interesting paper about the problem
• XFlat - a general tool for converting between definable "flat" formats and XML. (So not a particular syntax)
• XSCS - a paper describing something very similar to CompactXML above. I think.

Answer 2

If you're looking for a good way to simply view and make small tweaks, I would highly recommend simply getting a beautifier and a text editor with code folding. Personally I use notepad++, but I'm sure there's dozens of others with those simple capabilities.

Ironically, I'm on SO right now as a break from an XML file I'm working on with broken indentation. The original developer had the indentation working well (it's in a non standard language for which the libraries are poor) but subsequent developers have given it... less care than it deserves.