UPDATE: I’m really enjoying the Talk discussion of this feature. Also, at this point it’s better to talk about the feature than to use it. Everyone using it at once has the server that handles it taxed rather seriously!

A major publisher recently asked us to show them a tag cloud of their books. It took a mental flip, but only a few lines of code to adapt this for individual use.

The result is Tag Mirror, available from your and everyone’s profile—here’s mine (and Abby‘s, Altay‘s, Giovanni‘s and Casey‘s*). If you’re signed in, here’s yours. (Please note: It takes serious processing power to analyze 22 million tags. Everyone is going to hit it at once, so be patient.)

Tag Mirror “holds a mirror” up to your books and to you. Instead of showing what you think about your books—what a regular tag cloud shows—it shows you what others think of them, in effect using LibraryThing’s twenty-two million tags to organize and surface interesting topics from within your own collection.** As with other tag clouds, size equals importance. When you click on a tag, you get a relevancy-ranked list of books tagged that way.

I can’t decide if it’s just the sort of cherry-on-top feature that makes LibraryThing unique or if it’s something genuinely new and interesting. I think it might be the latter. As Altay put it, it’s the sort of idea that seems obvious in retrospect.

I didn’t know I was interested in gender studies.

Here’s a for-example. I don’t use the tags gender studies, patristics or theory. They’re just not terms I use. To some extent, that reflects who I am. But I have a fair number of books that, to others, fall under those categories. It’s interesting to slice my books up in an alien way—to see them through other eyes. Maybe I’m more interested in gender studies than I thought.

More concretely, I do use the tag “alternate history,” but browsing my tag mirror page called up some alternate histories that I hadn’t tagged that way—useful stuff.***

Finally, Tag Mirror gives everyone a tag cloud, even those who don’t bother to tag anything. It seems almost unfair.

As our recent discussion of what tagging does to knowledge brought out so well, tagging is a complex mixture of private purpose and public good. I agree with those who say that we tag best when we tag for ourselves. But when everyone does that, a rich web of meaning is created.

I’ve done my best to push tagging in some new directions, trying subjects and tags together statistically, making book recommendations based on tag patterns, and with the tagmash feature. You can add Tag Mirror to that list. Little things. But they keep getting more interesting.

UPDATE: It’s 4:30am and, of course, I couldn’t finish blogging it before someone else started a thread about it (“Just noticed this on my profile”). Come talk about it.

*Casey has a surprising number of cookbooks! He’s coming up here in a few weeks—it’ll be the first time any of us have actually met him. We usually just order pizza. I think that plan’s changed.
**It doesn’t actually exclude your own tags. They still have an effect.
***It also brought up Howard Zinn’s People’s History of the United States. People tag unexpectedly, if humorously.