[Yum] What is the yum comparison rule?

[Jonathan Ryshpan]

I build some of my own package, which I qualify with the distribution
string ".jon".  For example, I have built 
	k3b-debuginfo-0.12.17-1.jon
	k3b-extras-nonfree-0.12.17-3.jon
Yum does not want to update 
	k3b-debuginfo-0.12.17-1.jon
with
	k3b-debuginfo-0.12.17-1.fc6
which is available on one of the repositories I access.
But does want to update
	k3b-extras-nonfree-0.12.17-3.jon
with
	k3b-extras-nonfree-0.12.17-3.lvn6

What's the best way to prevent this.  Should I use a distribution string
of ".zzzz"?  Or is there something more reasonable looking?  An epoch?

Thanks - jon