This is problematic. Tag is not a "real" concept. Root is. At the very least, I would recommend returning the root in addition to tag. Once example of where this is a problem: http://finance.yahoo.com/q/op?s=GOOGL. Where the "Symbol" GOOGL maps to GOLG1 and GOLG8. The user probably wants to see the whole root and not just 1 or 8.