During my development of the .reo to .obj converter I investigated the .reo file structure and thought that it would be nice to have those kind of information packed in one place. Perhaps we could have it for the .rec files and other stuff too if applicable. So this .pdf document summarizes the whole .reo file structure. There are some problematic points which need more clarification so if you can help just post a reply.
** Updated the pdf on 10.August.2016 **
- version numbers indicate the protocol version of the .reo definition. The modeler only accepts models with version 2.0 - 2.2