Richard Stallman <rms@gnu.org> writes:

>     +;; The structure of `queue' is as follows
>     +;; ((question regexp closure . fn)
>     +;;  <other queue entries>)
>
> That shows the data's structure, but the structure
> is just the first part of documenting it.
> It's necessary to explain what each of the data _means_.

Here's another version with additional documentation on each part of
the structure.