This book constitutes the refereed proceedings of the 4th International Symposium on Unifying Theories of Programming, UTP 2012, held in Paris, France, in August 2012, co-located with the 18th International Symposium on Formal Methods, FM 2012. The 8 revised full papers presented together with 2 invited talks and one invited lecture were carefully reviewed and selected from 13 submissions.weiterlesen