In Potlatch 2 there are options under Buildings → Supermarket or Building. How should I tag a supermarket building? Should I choose Supermarket (shop=supermarket) for a building area with tag building=yes, or just tag the area with building=yes and then add a node with tag shop=supermarket plus other tags? Which is the preferred way? I saw this Tesco building http://www.openstreetmap.org/?lat=51.655711&lon=-0.269069&zoom=18 that uses supermarket on both a node and the area/way.