Namespace management in TeX is a co-operative affair: we all share one space,
so conventions such as \my@clever@macro are important. For LaTeX2e work, this
has always been done on a very informal basis: look around and find a space!
For LaTeX3, it seems like a good idea to make things a little bit more ordered.
We’ve therefore set up a simple flat-file prefix
register,
which will track all of the prefixes in use in expl3 code (provided people
tell us, of course).