Perhaps you know this, but other curious readers may not: it's worth noting (perhaps in an org-file) that properties such as tags, priorities and timestamps allow you to catalogue and access information without using the tree structure, so it can work for non-tree like structures too.

To any interested readers, I'd watch Carsten Dominik's (the original Org-Mode auhtor) Google Tech Talk on the topic. It's good to see it explained from the creator's perspective, imo.