digraph hierarch {
labelloc="top";
labelfloat=true
nodesep=1.0

node[shape=record,fontname=Ariel]
edge[dir=back,arrowtail=odiamond]

pset[label="{hamiltonian|+pairpot\n +estimator| name\n target\n wavefunction}"]
pairpot[label="{pairpot| | type\n name\n source\n target}"]
estimator[label="{estimator| | type\n name\n ... }"]

pset -> pairpot
pset->estimator
}