If there is, other than Wikitech-l, it should not be muddied with policy questions as well, as the page you link to is. I am not interested in how Wikipedia is going to categorize things. The interface I had in mind was basically a box on every category page, saying something to the effect of Enter a category to require: [____________________________] Enter a category to exclude: [____________________________] ( Submit ) Although the wording could use improvement. Filling one or both of the fields and clicking Submit would jump to a special page that would do the intersection, have a box to add/remove another category (or many of them at once). It would also list all categories currently represented, with little (X) links next to them to remove them from the result set. This would be the basic functionality. Additional stuff like a Suggestions button (to give a partial list of categories with nonzero intersections with the present category, preferably the largest ones) would be valuable and perhaps feasible additions, but there's no gain in trying to do too much at once.