Difference between DQM 4.0 and BODS 4.0

Please let me know how  DQM 4.0 and BODS 4.0 different than each other? I mean we can do data quality management through BODS then why we need DQM .Are both of them same? if not, in which scenarios we use DQM and in which we use BODS. Please provide an example.I am sorry if I am asking a silly question , but I am very new to these tools.