Tom recently sat down to work on some code that needs to analyze and handle variations in different versions of the HL7 messaging specs. So one of the interesting things he did was to create a spreadsheet that summarized the different message parts at different versions.
The spreadsheet shows each of the different message parts, with each relationship’s details spelled out over multiple releases. This is the first time I’ve seen something that summarized these differences so clearly; it struck me as a useful reference. It’s also interesting to see how, for all the churn that happens each release, the number of changes that have happened release to release has been relatively small.