chromium/docs/accessibility/browser/figures/single_process_system.gv

digraph graphname {
    graph [fontname = "helvetica", fontsize=11];
    node [shape="box", fontname = "helvetica", fontsize=11];
    edge [fontname = "helvetica", fontsize=11];
    rankdir="RL";

    subgraph cluster_browser {
        label = "Browser";
	dom_tree [label="DOM Tree"];
	dom_tree -> ax_tree;
	ax_tree [label="Accessibility Tree"];
    }

    ax_tree -> at [label="Platform Accessibility APIs"];
    at [label="Assistive Technology"];
}