Dagstuhl News January - December 2001

"Dagstuhl News" is a publication edited especially for the members of the Foundation "Informatikzentrum Schloss Dagstuhl" to thank them for their support. The News give a summary of the scientific work being done in Dagstuhl. Each Dagstuhl Seminar is presented by a small abstract describing the contents and scientific highlights of the seminar as well as the perspectives or challenges of the research topic

On switching classes, NLC-width, cliquewidth and treewidth

AbstractIn this paper we consider a connection between switching (of undirected graphs), and the notions of NLC-width, cliquewidth and treewidth. In particular, we show that the NLC-widths and the cliquewidths of two graphs in a switching class are at most a constant factor apart (2 for the former, 4 for the latter). A similar result can be shown not to hold for treewidth: it is easy to find a switching classes in which the distance between the lowest treewidth and the highest is dependent on the number of vertices of the graph. We also show that for NLC-width every width between the lowest and the highest of the switching class is attained by some graph in that switching class. We prove that this also holds for treewidth

Logic and Automata

Mathematical logic and automata theory are two scientific disciplines with a fundamentally close relationship. The authors of Logic and Automata take the occasion of the sixtieth birthday of Wolfgang Thomas to present a tour d'horizon of automata theory and logic. The twenty papers in this volume cover many different facets of logic and automata theory, emphasizing the connections to other disciplines such as games, algorithms, and semigroup theory, as well as discussing current challenges in the field