Top Ten Data Crunching Tips and Tricks
“Programs come and go, but data lives forever. Any time you’re working with data that isn’t in a well-documented standard format, you should therefore try to include format information in the data itself, so that it can’t ever be lost.” (Author: Greg Wilson, Source: ONLamp)
From a usability perspective this is excellent advice. I’ll admit the format you use might not make sense in terms of readability but with the help of a legend, those that wish to use your data will love you. If you can bake the legend into each data element, even better.