Sorry if I was unclear...

> It's basically the ability to specify access (rwx) on an individual and/or
> group basis.  It's conceptually quite simple.  How it's stored on disk is
> implementation-dependent and varies considerably.

I'm assuming that this is the bit you were thinking of porting from
freebsd, and so a summary of the implementation was what I was after.
Rick Kelly sent me a pointer to the src and essentially said that its
implemented as a separate filesystem - ufs instead of ffs?

I don't recall there being a concensus as to whether a new FS type
would be better...

As I mentioned - I like kre's "associated data" model - which could be
used to implement (the storage of) ACL's but is much more generic - so
hopefully each cool thing that comes along after ACL's could be
implemented without the need to introduce new filesystem types each
time.  I'm sure there are lots of details that need to be worked out,
but on principal - I like it :-)

Thanks
--sjg