Introduction Big Data Big data has attracted much attention from both academic and industry. Facebook:750 Million users Flickr:6 Billion photos Wal-Mart:267 Million items/day;4PB data warehouse oSloan Digital Sky Survey:New Mexico telescope captures 200 GB image data/day Science FOURTH PARADIGM data Li (http://cs.nju.edu.cn/lwj) Big Leaming CS.NJU 4/79Introduction Big Data Big data has attracted much attention from both academic and industry. Facebook: 750 Million users Flickr: 6 Billion photos Wal-Mart: 267 Million items/day; 4PB data warehouse Sloan Digital Sky Survey: New Mexico telescope captures 200 GB image data/day Li (http://cs.nju.edu.cn/lwj) Big Learning CS, NJU 4 / 79