How to merge edges in GraphViz

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If you are sketching out a node in graphviz which has many ancestors, a dense collection of arrow-heads can become unsightly:

Example 1 - Edges not merged

The code for the above graph is:

digraph G {
    {a, b, c} -> d;
    d -> e;
}

To merge the edges together, we can instead point these three nodes to an intermediate node, using edges without arrow. This example is adapted from the GraphViz FAQ (link).

This gives us:

Example 2 - edges merged

digraph G {
    d1 [shape=point,width=0.01,height=0.01];
    {a, b, c} -> d1 [dir=none];
    d1 -> d;
    d -> e;
}

To compile these examples, you can use an online tool such as Webgraphviz. If you have GraphViz installed, then run dot over them:

dot -Tpdf example.dot > example.pdf