Computing NodeTrix Representations of Clustered Graphs
  NodeTrix representations are a popular way to visualize clustered graphs; they represent clusters as adjacency matrices and inter-cluster edges as curves connecting the matrix boundaries. We study the complexity of constructing NodeTrix representations focusing on planarity testing problems, and we show several NP-completeness results and some polynomial-time algorithms. Building on such algorithms we develop a JavaScript library for NodeTrix representations aimed at reducing the crossings between edges incident to the same matrix. 
Giordano Da Lozzo, Giuseppe Di Battista, Fabrizio Frati, Maurizio   Patrignani
cs.CG cs.DS