Here are some interesting thoughts from The Swiss Army Librarian [http://www.swissarmylibrarian.net/2008/11/13/what-is-necessary-what-is-possible]:
” A little while ago, I got the idea to visually represent the official relationships that exist around a public library. Turns out, it was more involved than I thought, and the resulting figure wasn’t what I initially conceived.
This came about during a conference I attended. 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.”
The figure shown here (also below) is what I came up with (and evidence of my mad graphic design skills). The center triangle are the relationships between the public library (in blue, in the middle), the people we serve (on the top) and the people who serve us (on the bottom). The two big arrows on either side are the flow of needs and reality – somewhere in the middle the public library is trying to reconcile the two…”