This is a better solution than creating faceted single tags (e.g., “arthistory:france”) that I made a while back because (a) it’s simpler, and (b) it doesn’t require any sort of mechanism for agreeing on a taxonomy of facets. If you want to search Flickr for French art and not get a billion pictures of family vacations in France, you can search for the “France” tag and pivot on the “art” tag.To try it out, take a look at this fac.etio.us result for the “education” tag. In addition to seeing all posts with that tag, you can also drill down by selecting from the list of other tags on the education-tagged posts. I see, for example, that some of the posts tagged with “education” also have an “art” tag. By clicking on that tag link, I get posts that contain both tags. It’s like a boolean search, but it also gives me discoverability, since it provides a list of other tags that produce a non-null search result. Likewise, I can pivot on information about the post creator, the site, the feed, and/or the date.