Learning ConTeXt: \setupitemize

[Gary Pajer <pajer@iname.com>]

I'm learning ConTeXt, and I've chosen to beat up on \setupitemize to see how
things work.
(If the answers to my question are in some doc somewhere, please tell me
where it is!)

Consider the file below.  I expected to see a hairline above the second
itemization, and indeed I do.  But if I remove the "columns" specifier, the
hairline does not appear.  Is this the correct behavior, or a bug?

Also:  what does the keyword "beforehead" do?  If I replace "before" with
"beforehead" in the example, I get nothing.     Is it in the docs somewhere?

In the lists of keywords for many commands there are parameters listed that
I can't figure out.  Some of them seem to do nothing, but I always wonder if
they only operate in conjunction with some other feature, or I haven't
implemented them correctly.  Some of them do something, but I can't figure
out what the rule is.  Is there a doc somewhere describing the keywords?  Is
it in the manual and I've missed it?

Thanks,
Gary Pajer
ConTeXt 2003.3.9 / up-to-date MikTeX / Win98
-----------------------------------------
\setupitemize[1][n]
\setupitemize[2][a][before=\hairline]
%
\starttext
%
\startitemize
\item Level One
%
\startitemize
\item first
\item second
\item third
\stopitemize
%
\stopitemize
\stoptext