With all the cross-pollination going on between Western styles of dance--ballet, modern, and jazz borrow liberally from one another--it can be hard to define what makes a form unique. But it's safe to say that if jazz dance were a punctuation mark, it would be the exclamation point. Consider the Koresh Dance Company from Philadelphia, one of 15 companies appearing in the four-day international festival of performance that caps the Jazz Dance World Congress. Its highly dramatic Facing the Sun, choreographed by Israeli native Ronen Koresh, has an apocalyptic feel as a phalanx of dancers confronts a powerful beam of light that first flattens them all at once and then, after they recover and confront it again, flattens them one by one. Mostly danced in unison--which tends to create a more forceful, less nuanced impression--the piece has the sort of one-to-one correspondence with the music and lighting that ensures no point gets lost; the last dancer falls, for instance, on the score's last note. But the universe of jazz dance is large and getting larger, as other pieces attest. Japan's Masashi Action Machine presents Japanese Businessman, about contemporary daily life, and Gunjyo, about the essence of the sea. Robert Battle's Battleworks, based in New York, offers Takademe, which draws on African and Indian dance as well as tap and Michael Jackson's moves. African-American dance is represented (Muntu Dance Theatre of Chicago), as is tap (Chicago's M.A.D.D. Rhythms). The Joffrey Ballet performs the pas de deux from Jerome Robbins's 1958 N.Y. Export: Opus Jazz, and Hubbard Street 2 offers Millicent Johnnie's Dirti Rok, which looks at the evolution of dancehall and reggae music. Each evening is a completely different program; see the listing for details. Wed-Sat 8/3-8/6, 8 PM, Harris Theater for Music and Dance, 205 E. Randolph, 312-334-7777, $45.