WITH EACH NEW VERSION OF A BIENNIAL, be it an established institution or an upstart like Berlin's, a simultaneous weaving and unraveling often takes place. As on Penelope's loom, a new texture arises. Various mechanisms may seem inescapably embedded in the process—the close adherence to a municipality (rather than its lived local context); a certain number of artists (thirty being the apparent minimum; maximum as yet unknown); and invariably, too few new commissions—but that's not necessarily to suggest that what's known as a biennial is a preordained operation. The success of a biennial