digraph ripple_annot {
	rankdir=LR
	abs [label="abstract model" shape=box height=2 color=red]
	sch [label="concrete model\n(schematics)"]
	pcb [label="pcb layout,\nsilicon, etc"]
	sim [label="simulation"]
	bom [label="purchase management\n(BoM, parts, vendors)"]
	doc [label="documentation\ne.g. user manual"]

	abs->sch
	sch->abs [weight=0]

	abs->pcb
	pcb->abs [weight=0]

	abs->sim
	sim->abs [weight=0]

	abs->bom
	bom->abs [weight=0]

	abs->doc
	doc->abs [weight=0]

}