NEW YORK -- One recent misty morning at Rockaway Beach in Queens, midway through the installation of six artist-designed Ping-Pong tables on the sand, Gabriela López Dena from Public Art Fund said: "I have nightmares where the ocean comes and washes the exhibition away!" López Dena had been up all night in the rain supervising a crane hoisting these new commissions, conceived to withstand heavy use and the harsh environment, as well as soft serve the artists' ideas about the democratic...