vcg specification is in vcg.ads
vcg body is in vcg.adb
vcg.producevcs subunit is in vcg-producevcs.adb
vcg.producevcs.buildgraph subunit is in vcg-producevcs-buildgraph.adb
vcg.producevcs.buildgraph.buildannotationexpndag subunit is in 
    vcg-producevcs-buildgraph-buildannotationexpndag.adb
vcg.producevcs.buildgraph.buildexpndag subunit is in 
    vcg-producevcs-buildgraph-buildexpndag.adb
