Nominations for the best XML markup language of all time

Hi Folks,

What XML markup language do you consider to be the best ever?

Here's my nomination.

First I define "best." 

The best XML markup language:

1. Has a significant marketplace penetration.

2. Is small and is specified in relatively few pages ( < 50 ).

3. Is simple and readily understood.

4. Consists of markup that can be assembled in various ways to create richly complex markup structures.

5. Has (markup) assembly rules that are consistent, with little or no "exceptions to the rule."

6. Has a formal basis underlying it.


Okay, now for my nomination. For the best XML markup language of all time I nominate:

        RELAX NG

/Roger