In the year 2012, which conference had the most papers presented? Give the short name of the conference.
Papers refers to Paper.Id; short name of the conference refers to Conference.ShortName
SELECT T2.ShortName FROM Paper AS T1 INNER JOIN Conference AS T2 ON T1.ConferenceId = T2.Id WHERE T1.Year = '2012' GROUP BY T1.ConferenceId ORDER BY COUNT(T1.Id) DESC LIMIT 1