I stumbled across this site earlier and thought it was a bit more similar to what I want to build. The transaction page (just going off the demo video) is a simpler, though–transactions can only have one category. I definitely want to support multiple tags per entry.

I’ve also been thinking about other ways to do the tagging. Traditional tagging works pretty well, but I want to have the ability to create as many interesting charts as possible from one dataset. The system should be smart enough to know that pizza is Italian Food. It should know that Italian Food is food. After searching for various things like “complex tags” and various synonyms, I found nothing. My friend Annie recommended the search string “hierarchical tagging” and that at least yielded a few cool resources. There’s a guy at Stanford whose doing research on it, though after reading his paper it seems like he’s trying to detect the structures from an already existing set of tags.
I don’t really care about generating this data after the fact…I’m fine with doing a little legwork up front. It gets kind of messy, though (can you say many to many relationship?). Should it also know that Pizza Hut is a type of Italian Restaurant which is a Restaurant? Should entering Pizza Hut automagically enter a tag for pizza?

The other big question… is this relationship something that exists only in the database? Or does entering the tag for Pizza automatically populate it with the superTags? This seems like it would certainly make simple lookups quicker.

I’ll have to noodle it for awhile longer.