Creating Image Diagrams similar to JSON

I've seen it done in several books a开发者_如何学Pythonnd such, so there has to be something that is generating them, or I'm just outright not seeing the tools in Visio, but I was wondering if anyone knows how to make diagrams similar to the ones commonly seen in regards to JSON.

Example Seen Here : http://www.json.org/object.gif

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• http://dotnet.jku.at/applications/Visualizer/
• http://www.informatik.uni-freiburg.de/~thiemann/haskell/ebnf2ps/
• http://karmin.ch/ebnf/index

It doesn't have anything to do with json, it just takes a grammar spec and renders it visually.