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.

We've been hoping for something much more user-friendly, such as check-boxes next to each category listing on a page, and a button that says something like "find articles with checked categories". Of course you could have a special page for the more techy users that functions as Simetrical has laid out above, or that page could be the destination for displaying the initial intersection results so it can be refined more. Possible interfaces are discussed at [[Wikipedia:Category intersection]] (or the shortcut [[WP:CI]]). I can repost here, the relevant non policy stuff as things develop.

-- Samuel Wantman [[en:User:Sam]]