He had set out to represent graphically the complexity of flow in the library services hierarchy. Here's what he came up with:
I'll let him speak for himself:
I was thinking about library services, and why some good ideas get implemented while others don’t, and why libraries offer some things that seem to be of no use to anyone. This started me down the path of getting to the root of “why” and “how,” which I came to refer to as “What is Necessary” and “What is Possible.”Check out his blog post.