Word description Constructs a cluster, which is a subgraph whose id begins with the word "cluster".
id must be an object supported by the present word. The string "cluster_" is automatically prefixed to the id of the resulting subgraph.
Notes Clusters are just a syntactic convention. Not all Graphviz layout engines treat clusters any differently from regular subgraphs. See the Graphviz documentation ( http://graphviz.org/Documentation.php ) for more information.