The only "alternative" I see here is that clicking on successive tags in the UI adds an AND query. In Blue Dot this is done (manually) by typing in more than one tag in the search box; e.g.

"tag:design tag:css"

I think this has some uses when people start to build larger data sets. But the most common query is to want to "pivot" to the new tag when the user clicks on another one. But, something interesting to think about for a future feature for more sophisticated tag browsing UI.