Comment 1 for bug 268143

Weak ("maybe") dependencies are also present in yum comps:

https://launchpad.net/~afb/smart/groups

The Depends equivalent there have type="mandatory", whereas
the Recommends equivalent has type="optional" instead. There's
also "conditional" that depends on which other packages and
selections have been made, and are sorta complex that way:

      <packagereq type="conditional" requires="openoffice.org-langpack-en">openoffice.org-core</packagereq>