They don't conflict. They are both applied. <base> is the document's base URI, and xml:base is the base URI of the element it is applied on.
What about: <base href="http://www.example.org/" xml:base="/bar" /> ? -- Asbjørn Ulsberg -=|=- http://virtuelvis.com/quark/ «He's a loathsome offensive brute, yet I can't look away»