The first of OBC's two semicentennial celebrations takes a look back at its past while also giving a glimpse of its future: The program includes repertory excerpts of the company's early ballets that followed in the influential footsteps of Sergei Diaghilev's Ballets Russes — as well as highlights of revivals by OBC founder Ronn Guidi and others — then closes with a survey of new works by Val Caniparoli, Betsy Erickson, Michael Lowe, Robert Moses, Amy Seiwert, and current OBC Artistic Director Graham Lustig.