Organization/Foundation - Topic
Category - SubCategory - Topic
City - County - State (not high pri, but if/when people are building out new states)
others?
parent/child/sibling relationships among patterns - http://grouppatterns.wagn.org/wagn/Celebration
(workaround for sibling; harder because it's symmetrical: see http://grouppatterns.wagn.org/wagn/peers+*rform )