I was thinking about this a while ago when I was writing my own personal finance software. Rather than embedding any notion of hierarchy, I allow all transacti

I was thinking about this a while ago when I was writing my own personal finance software. Rather than embedding any notion of hierarchy, I allow all transactions (regardless of the source) to have an arbitrary number of tags. Hierarchy is simply the conjunction of sets of tags. I can easily re-tag transactions and rollback tagging schemes. Seems to work well for all of the processing I want to do.