Exports format

[*Hobbit*]

Is there a "standard" anywhere of

a> the format of an exports file, and what fields are actually supposed to
   be read for what purpose, and/or

b> what one can and cannot export from a given machine?

I have two examples of flagrant INCOMPATIBILITIES I can point to with
regard to these -- point a is demonstrated by a 4.1.1 SunOS which won't
let hosts given in -access=hostname mount it, but will let hosts given in
-rw=hostname mount away;  point b is demonstrated by our 3.0 Ultrix which
lets you export little pieces of an already-exported filesystem to
different machines.

The Ultrix behavior violates what the Sun manpages claim, but it's
actually VERY useful to us.  Unfortunately none of our other Unix boxes do
this, so we're stuck with lots of crap on our poor little overloaded
microvax.

Sorry if this duplicates any recent discussion, but I don't read this
group regularly.  Thus, replies directly to me, please...