digraph {
  rankdir=LR;
  fontname="sans-serif";
  compound=true;
  node [shape="box", style="rounded", border=0, fontname="sans-serif"];

  subgraph cluster_graph2 {
    style="rounded";
    color="lightgrey";
    label = "example:B"
    tooltip = "example:B"
    fontsize=10;
    item2[label="example:item2",tooltip="example:item2"];
    type2[label="rdfs:Resource",tooltip="rdfs:Resource"];
    item2 -> type2 [label="rdf:type",fontsize=10,fontname="sans-serif",tooltip="rdf:type",labeltooltip="rdf:type"];
  }

  subgraph cluster_graph1 {
    style="rounded";
    color="lightgrey";
    label = "example:A"
    tooltip = "example:A"
    fontsize=10;
    item1[label="example:item1",tooltip="example:item1"];
    type1[label="rdfs:Resource",tooltip="rdfs:Resource"];
    item1 -> type1 [label="rdf:type",fontsize=10,fontname="sans-serif",tooltip="rdf:type",labeltooltip="rdf:type"];
  }
}