The value indicates whether to treat a node whose name has the form |edgelabel|* as a special node representing an edge label. The default (0) produces no effect. If the attribute is set to 1, sfdp uses a penalty-based method to make that kind of node close to the center of its neighbor. With a value of 2, sfdp uses a penalty-based method to make that kind of node close to the old center of its neighbor. Finally, a value of 3 invokes a two-step process of overlap removal and straightening.