Hello,
I have been playing around with Hierarchy analysis and yEd graph editor with some interesting results. I believe graphML could become a very nice API to document VI hierarchies especially when coupled with yEd and its web interface tools etc. Here is the hierarchy analysis of the moon landing NI example.
You can switch graph types at the click of a button, filter / colour different elements by type etc, select partial neighbours of the hierarchy ... the possibilites go on.
graphML is XML based so is pretty easy to do.
Craig