The name of the node the edge leaves.
The name of the node it arrives at.
Whether it was written -> (a digraph) rather than -- (a graph).
OptionallabelWhat the drawing says on the edge -- its label, xlabel, headlabel
and taillabel as drawn -- joined by spaces, or undefined when it says
nothing.
The edge's group.
One edge Graphviz drew: a
<g class="edge">.