An operation of concatenation is introduced for graphs. Then strings are viewed as expressions denoting graphs, and string languages are interpreted as graph languages. For a clas...
Streams are acyclic directed subgraphs of the logical ow graph of a proof representing bundles of paths with the same origin and the same end. The notion of stream is used to desc...
We show that there exists a linear time algorithm for deciding whether a graph of bounded tree-width has clique-width k for some fixed integer k. Communicated by Giuseppe Liotta ...
A coloring is proper if each color class induces connected components of order one (where the order of a graph is its number of vertices). Here we study relaxations of proper two-c...