Mandy 8.1 uses something called URPMI which does a pretty good job. Plain ol' RPM has a database of what is installed, so checks can be made to see if dependancies have been met, or not, but it doesn't have a database of what can be installed. This would be damn hard as the collection of RPMS is huge.
URPMI goes some-way to doing the latter, but not entirely. By default a database of what is on the installation CDs is given, but you can also make a database of what's on Mandy's FTP site, and there are even commands to make databases from your own RPM collection. It's quite useful, but it won't install the dependancies unless you tell it to. If you're running Mandy already, then use the Software Manager instead of the Package Manager to take advantage of URPMI.