Those are options rather than requirements.  For
example, I will almost always fill in a newsgroup
name, unless I'm not sure which newsgroup
might have the information I want (e.g., if I have
a computer question).   But after that it depends
on the information I'm seeking.  I might be
interested in all posts posted in the last week in
a particular newsgroup.  I would limit the dates to
the last week and then run my search *without*
specifying a topic, or an author.  I almost never
specify an author, but if I had a specific cat health
question, I might start by specifying Phil P. as the
author.  Or I might be interested in a particular
topic, say CRF, and not worry about dates.
That would result in a lot of posts coming up,
but then you can do an additional search to add
more limits.

As an example, say I was interested in outdoor
enclosures.  In the advanced search I put
"outdoor enclosures" in the blank for Find
messages with all the words.  I put r.p.c.h+b
in the group blank.  I changed the start date
to 1 Jan 2006 because I don't want to wade
through a gadzillion posts dating back to 1981.
The search showed that in the last year there
were 6 topics on outdoor enclosures.  A
good start, and I can modify my search from
that point.

Gail F.