What is the difference from existing schema definition langs?

[ddosia]

Hi there! Quite interesting project, but it would be great if you'll enhance README with few keystrokes how it is differs from existing schema definition languages (e.g. http://json-schema.org/)?

At some point I was interested in json-schema, and although it is well thought project with variety of libs, it still have undefined behaviours (google groups of json schema will clarify what I mean).