I've read a lot of the NI patents[*] with respect to LabVIEW and I don't remember the heirachy being in them. Just about everything else is there including the underlying structure of a VI, dataspaces, icons, connector panes, VI flow diagrams, etc, but not VI heirachy diagrams. That said, it's more than possible that I may have missed that page of that particular patent...
[*] ok, so I'm a geek - but you'd be amazed with what you can learn about LabVIEW's underlying engine by checking them out - I highly recommend it for those who prefer to understand the engine before complaining about it . When you've got a lunch hour to spare and a good cup of tea, here's some of the more interesting ones to check out - I suggest you start form the bottom and go straight to the images section. Of course, some of the patents are more inspired than others