[CentOS] Groups and rpms

yum grouplist is almost ok for learning what groups are 
available.Though it does not distinguish between base/manditory and 
added in the installed list.

But yum list is not really helpful.

I would like to see something of what rpms are within what 
group.  then what rpms are not in any group.  And which groups and 
stand-a-lone rpms are base.

maybe it can be teased out of comp.xml...