How does it work: What package can open a file?

[Richard Shaw]

When you try to open a file for which you have no package installed
that handles that file type, there is a GUI that pops up and asks if
you want it to search for a package that can handle the file.

How exactly does this mechanism work? I'm assuming there is some
meta-data in the RPM package that provides this information?

I'm trying to help fix a package which does support a particular file
type but doesn't come up in the list of potential packages.

Thanks,
Richard