The tricky part is, what do you do when your data doesn't fit into a tree?
You have a folder of photos from that trip to Costa Rica, and you use one of them in a design project. Do you leave the photo in the Costa Rica folder, or do you move it to the Images subfolder in your project folder? Or do you keep a copy in both? Does it bother you that your computer is storing the same data, in two places, redundantly, simply because it can't comprehend the idea that a resource could be relevent in two places?
The relational model solves that problem, but at a certain mental cost. It is not particularly expensive, it is just a mental mode that people in western society are not used to using- It is a verb oriented model, rather than a noun oriented model. We are used to nouns. Things just are this way, that way, the grass is green, the house is brick, the cheetah is a cat, the platypus is a trieme.
okay so what's the relational model about? Most technical people will tell you it's about tables, but that's rubbish. Ignore them. The idea behind the relational model is that instead of organizing data based on what it *is* or *has* or *belongs to* by arranging it in a heirarchy, you instead describe how it is related to other things. So that photo was *Used* in project b, and *taken* in costa rica. Costa Rica was *photographed* by Dayne, Dayne *created* these photos. These relationships create links between your bits of data, big and small, like photos, or documents, or names, or places.
so how does navigation work? when you want to find all the photos from costa rica type in
get place:"costa rica", photo
if you don't like typing, such queries can easily be created point and click style, with the data that's already in there.
get -> place -> costa rica -> photo
put person thailand person
edit thing denver place
create design arizona thing
Then the system works out automatically what "costa rica" and "photos" have in common.
I really like the relational model, and I really hate categories. Yeay verbs, boo nouns. Yeay relationships, boo heirarchies.