Last year, when I reviewed The Sum of Parts, the community-oriented piece produced by Connect, Sadler’s Wells Creative Learning department, I thought it wouldn’t be possible to do any better. Well, I was wrong, as this year’s Compass was an even more breathtaking experience. The new project, which involves more than 100 non-professional performers and a unique roster of artists, has been conceived at a time when World Cities 2012, Pina Bausch’s retrospective of works devoted to cities and cultures from around the world, is imminent.