STACS 99

The Symposium on Theoretical Aspects of Computer Science (STACS) is held annually, alternating between France and Germany. The current volume cons- tutes the proceedings of the 16th STACS conference, organized jointly by the Special Interest Group for Theoretical Computer Science of the Gesellschaft fur ¨ Informatik (GI) in Germany, and Maison de l'Informatique et des Math e- tiques Discr etes (MIMD) in France. The conference took place in Trier { the oldest town in Germany, with more than 2 millennia of history. Previous symposia of the series were held in Paris (1984), Saarbru ¨cken (1985), Orsay (1986), Passau (1987), Bordeaux (1988), Paderborn (1989), Rouen (1990), Hamburg (1991), Cachan (1992), Wur ¨ zburg (1993), Caen (1994), Mu ¨nchen (1995), Grenoble (1996), Lu ¨beck (1997), and Paris (1998). All proceedings of the series have been published in the Lecture Notes of Computer Science series of Springer-Verlag. STACShasbecome oneofthe mostimportantannualmeetingsin Europefor the theoretical computer science community. This time, altogether 300 authors from36countriesonv econtinentssubmittedtheirpapers.Eachsubmissionwas sent to v e members of the program committee for review. During the program committee session 51 out of the 146 submissions were accepted for presen- tion. In two of the selected papers the same result was proved independently.