What’s the difference between a category and a tag?

I’ve been asked that question a number of times, and the answer always escapes me. Reading that Microsoft will be redesigning their Xbox interface, dropping fixed sections and adopting a non-hierarchical structure reminded me of tags vs. categories. Now I think the difference between the two is paradigm sized.

Gmail calls them labels. Flickr calls them tags. In both cases, they’re simply ID pins you put on anything you feel fit together. For instance, you might put a label called “music” on both Sonic Youth and Rihanna content, but an additional label called “outstanding” would only be tacked on to the former. Categories, on the other hand, approach things differently and discriminate content into hierarchical sub-categories. The idea is that a tree-like structure allows for more directed browsing of the categorized contents.

As such, the most elaborate difference between tagging and categorizing content is the ad-hoc nature and lack of hierarchy inherent in tagging mechanisms. Tags are born equal and earn their fame with repeated use. This encourages the creation of many more tags than you would create categories, further refining casual users ability to drill through the depths of specific content.

Because of the casual nature of tags, the creation of single-use throwaway tags is not a problem. The more tags, the better¹—so much that it might even make sense to allow end users to tag your content. Think about it, users plow through your Mariana Trench deep archive leaving little golden crumb trails in their wake.

Tags are the cake and the whipped cream of usable future interfaces. I find that a safe bet.

When tagging mechanisms are added to various content exploration interfaces, quite a few things become immediately obsolete. Any hierarchical structure such as folders become near-worthless when you can see the “folder contents” of your choice by simply clicking the appropriate tag. The mystery meat discoverability problems inherent in having hidden subfolders go the way of the dodo; in its stead is a marxist non-hierarchy.

The requirements for tags seem simple: a flat structure and scalability. Of course, simplicity is no simple thing.

For one thing, the flat structure of tags begs the question from the couch potato: which tags are the good ones? Sizing up tags according to usage popularity—tag clouds—only lets us know which tags have the most content. Picking out the ones that hide the good stuff requires a human editor.

The other thing, scalability, doesn’t come easy. For a moment, let’s forget the fact that categories are usually lists, just like tags, and instead visualize a finite number of sections. Because each section of an interface can hold content according to its section title, sections can be compared to parent categories. When there’s a finite number of sections, we can design them like tabs or stacks or whatever physical metaphor you can think of. Now what if we need a new section but we’ve run out of room? Well you’d be screwed and you should have designed a scalable interface. Enter the PlayStation and Xbox dashboards.

The PlayStation 3 dashboard uses a cross media bar, or XMB for short. The XMB consists of a horizontal line of icons floating in space, as many icons as are needed. Highlight one icon and another list of icons will cross the bar, allowing you to select sub contents vertically.

The current Xbox dashboard, on the other hand, uses a blade-like interface; tabs span the height of the screen and sections are selected by flipping left and right. Like with all other section-divided interfaces, the amount of room for sections is finite, hence putting quite the responsibility on naming those sections. Have you tried this interface? Where would you look for downloadable games; In “Xbox Live”? Or in “Games”? Suffice to say, discoverability is low and scalability virtually non-existant.

It seems, however, that Microsoft, come next Xbox system update, will be switching to a scalable interface to the system.

Could this be the contents of a Halo tag?

Instead of the finite amount of blades, the Xbox will sport a Playstation XMB-like cross-navigation system allowing for an infinite amount of vertical and horizontal sections. While the not-entirely-flat structure will require some drilling, at least the potential will be there to create clever, throw-away content-hubs that simplify finding content. Microsoft calls this the “New Xbox Experience”, and they think it’ll do well in Europe. I say it might. But it all depends on whether they dare use this new tag-like, flat and scalable interface structure the way it should be used. That is, like you would use tags and not categories.

The difference between a tag and a category is that one tries to organize chaos and falls flat; the other accepts chaos and deals with it.

1. To a certain degree, of course. As with all good things.  ↑