Gene Smith has posted a helpful diagram from his IA Summit Panel presentation:

Click to see full size

You get folksonomies when people are tagging stuff — whether it’s their own or other’s — in public.

Thomas Vander Wal, who coined the term “folksonomy,” I think would label the X axis [Mnemonic: X is a-cross] differently. In his post on broad and narrow folksonomies, he defines a broad folksonomy as one that “has many people tagging the same object and every person can tag the object with their own tags” (= del.icio.us). A narrow taxonomy has fewer people tagging and there is only one of each tag applied (= flickr).

The latter clause is the important one. At del.icio.us, 100 people could upload the same bookmark (= URL) and tag it. At flickr, generally only the person who took a photo is going to upload it, and even if two people upload the identical photo, flickr counts them as a separate. So, at del.icio.us, if 50 people have tagged a bookmark as “SF,” you may nevertheless decide to become the 51st, because that’s how you want to remember that URL. That there are now 51 “SF” tags is important information that could be used to create a folksonomy. At flickr, if you come across a photo of the Golden Gate bridge that is already tagged “SF,” and that’s how you want to remember it, you won’t add a “SF” tag because the photo already has that tag. Thus, flickr doesn’t know how many people find the “SF” tag useful for any particular photo. (Flickr can know that overall at flickr there are lots more “SF” tags than “San Francisco” tags; the folksonomy happens one level up.)

So, if I understand Thomas, a broad taxonomy is really one in which an object can have multiple instances of the same tag, whereas in a narrow taxonomy, an object can only have one instance of each tag.

I wrote to Thomas and asked him how he would jigger Gene’s diagram, and he replied:

I think the X-axis should be tagging for one’s self (right) and tagging for others (left), which would make the pure folksonomy quadrant the upper right. This would move GMail to the lower right with Furl above it and a little left. I think Technorati Tags would move ever so slightly right.

Or we could replace the X axis with Narrow to Broad folksonomy, which would move flickr to the left and del.icio.us to the right. So, now all we need is a n-dimensional matrix to accommodate all these damn quadrants. Plus, I need a brain that understands spatial relationships.