As I have explained in my presentation about Social Distributed Classification at the Italian IA Summit these year,the main issue about actual tagging is that the usability of tag clouds is very very low.

After having reached the zero level of classification complexity through tagging, we have now to reintroduce a little of structure to improve usability and findability.

The structure can be introduced gradually and in a bunch of different ways.

Hierarchies are one of the ingredients and provides:
- serendipity improvement
- browsability enhancement
- better comprehension of tags’ meaning

Hierarchies can be introduced by users themselves or using a clustering algorithm as already done by RawSugar and Edgeio.

Now I understand what you are referring to - using this flexible hybrid organization method applied to applications like a Reader or Email client.

Some good discussions, including mine, can be found here, here, and here.

I would, however, caution against making things too complicated. I am a firm believer that we “find” ina variety of ways - some rather just go to the search box, others organize in such a away that they need a solid hierarchical organization.

You refer to a hybrid organization seemingly because you remove “search” as in a search box from the equation.

However, if you refer to my post on this issue, it seems to me that if we are careful to construct “smart” folder hierarchical organizational schemes (triggered by keywords/labels/tags), then we would simply need to tag items and not worry about hierarchical structure.

Case in point: I have 17 GMail labels (really just tags). I’m very reluctant to add new labels because they aren’t organized and the listing already scrolls off my screen. Hierarchical tagging would let me categorize some labels/tags by work, personal, family, online accounts, etc.

In an RSS Reader, or an email client, or whatever, I would like the flexibility of tagging AND dynamic, cross-listed categorizing.

For example, your Flickr example does combine the two, but only the owner of the image can create the set, but if given appropriate permissions, anyone can tag the image. Tagging is more social because it could potentially allow anyone to apply descriptors to an object.

I’m not sure what the benefit is to combining the two for reasons surrounding syndication, because the subscriber is at the mercy of whatever organization scheme the owner decides to employ. Choosing a syndication by hierarchical category or tag is already available.

Also, tagging may be messy, but it lends itself to find by search rather than find by navigation. Translated to syndication, I’m not sure what the benefit is. If I find a tag or if I find a hierarchical category, I may subscribe to it.

Right now what you describe only seems like hierarchical organization, with some categories cross-listed. Is there something I am misunderstanding?

We organize browser bookmarks in folders. You probably organize your RSS/Atom feeds in some sort of folder structure. Your Flickr photos are both tagged and placed in Sets. Why would a simple mechanism to categorize / specialize your tags be dangerous?

In any case, I can’t take credit for the idea… a lot of people are exploring the concept (Google “hierarchical tagging” to see). I’m just looking for an easy way to realize it.

See Keith’s “Three Breadcrumbs Overview” over at User Experience dot org.