At my last job, I worked with data from the Brazilian educational system in several situations. The details aren’t the important part, but the format – a giant denormalized CSV with an accompanying PDF detailing its fields. It is very nice after you work with it for some time, but there are some things that could be better.
In that format, enumerations (fields with a fixed, finite set of values) are encoded as some arbitrary integer range, boolean values as 0 or 1, and other implementation details that are explained in the PDF. Thus far we have a cute CSV with documented fields. Nice, right?