Here you will find the formal specification for each version of the dr4 document structure. The most important information in the specification are the data types supported within data rows. Other components of the specification relating to the document arrangement is unlikely to change between versions.
All versions consist of three numbers, ranging in value from 0 to 255. The left is the most significant versioning number, while the right most, the patch number, is the least. The version numbers directly correspond to the version bytes in the dr4 document header.
For more info on the document format, see the format page