Before the idea is dismissed entirely, I believe forms within forms
can make sense. An inner form would inherit all the input fields of
all containing forms. (This is similar in some ways to allowing
multiple submit buttons each with a slightly different behavior.) This
would allow the user to fill in some fields that are common across
several alternative sets of additional fields. One could just put all
these alternative fields in one top level form after making sure that
there are no conflicts in field names, but I think nested forms permit
a cleaner solution.
Along with nested forms, it would also be nice to support
showing/enabling and hiding/disabling of fields that apply/don't apply
because of some higher level selection by the user. This is moving in
the direction of more and more interactive GUI features, but there is
alot more that needs to be worked out in this regard. If you are
interested in this direction, I recommend looking into the interactive
image format by the Blue Skies folks at U of Michigan (sorry I don't
have a URL).
Daniel LaLiberte (liberte@ncsa.uiuc.edu)
National Center for Supercomputing Applications
http://union.ncsa.uiuc.edu/~liberte/