May I suggest that there are two types of rests (Ger. Pause; Fr. silence)
- exact and inexact? Exact rests must be strictly observed, inexacts not.
Much of it has to do with keeping the overall pulse of the music.  Hence,
a rest at the end of a piece or between sections is often not given its
full duration, with little harm done.  Needless to say (but I'll probably
have to say it anyway, so why not now?), there are also rests that occur
in such contexts that should be fully observed.  Performers must actually
think about it, rather than simply follow.

Steve Schwartz