“Dance revivals come in many forms and get sketchier the further one recedes in time. Music has a long-accepted system of notation; theater has texts. Dance has the memories of the choreographer (if still alive) and his or her disciples, who fan across the country and the world recreating works in which, often, they once danced. So why do them at all? In dance, we live in a time, or so many people fret, of diminished choreography: there just aren’t that many great dance-makers out there, especially in classical ballet. Hence the desire to freshen the repertory by mining the past…”