Allow mixed AND-OR queries

It would be very powerful if you could specify a number of terms within each vocabulary and use OR to combine them within the vocabulary, but use AND to combine searches between different vocabularies.

As an example, suppose we have vocabularies VEGETABLES(carrots, onions, potatoes) and LOCATION(britain, us, france). These are two orthogonal (independent) vocabularies.

Now suppose we want to find articles about carrots or potatoes from france. At the moment the All Terms option will fail to find anything unless it mentions both carrots and potatoes, while the Any Terms option will also find articles about American potatoes and French onions. Neither is quite what we want. Although we could make a great stew.