Thevolumecomprises?nalversionsofthepaperspresentedatthe5thInternat- nal Andrei Ershov Memorial Conference Perspectives of System Informatics, Akademgorodok (Novosibirsk, Russia), July 9 12, 2003. The main goal of the conference was to give an overview of research directions that are decisive for growth in the major areas of research activities in system informatics. The conference was held to honor the 70th anniversary of Ershov s closest colleague, the late Prof. Igor Pottosin (1933 2001), and his outstanding cont- bution towards advancing informatics. The ?rst four Andrei Ershov conferences...