Two packages interdependency issue

[Tomasz Buchert <tomasz.buchert@inria.fr>]

Hi,
I had no idea what subject to pick up. I hope
it will attract somebody. :D

I have a source package (stellarium FYI) and I want to
create a new source package that contains packages that
will be *optional* for stellarium (stellarium-stars, i.e.,
additional stars for stellarium). The additional star
packs don't change very often and therefore I would prefer
to keep them separate from stellarium source package for the sake
of simplicity and more meaningful version numbering.

The problem is that, even though they are optional, a particular
version of stellarium may require a particular version of star packs.

For example, assume we have the following packages installed:

   stellarium-1.0
   stellarium-stars-4.0

Now we install stellarum-2.0 and we have:

   stellarium-2.0
   stellarium-stars-4.0

However, the version 2.0 changed format or something and will not work properly
with stellarium-stars-4.0 and requires, say, a version 5.0 of stars.

How can I model this using package relationships? The closest one I see is
"Conflicts: stellarium-stars (<= 4.0)" in stellarium's 2.0 control file.
Is there a better way?

Cheers,
Tomasz Buchert