Those who are starting to explore diagrams, organization charts, flow charts etc. would do well to start here. Graphviz does lots of tricks but the simplest is the directed acyclic graph or DAG. Before you run away, a directed graph at its simplest relates two "things" such that one leads to another, e.g. a->b or a leads to b. Think "flipping the switch turns on the light". The part of Graphviz that takes the left side leads to the right side statements is called "dot". Pretend you are Aristotle expounding on causation or a preacher drawing the creation process from Genesis.

Dot turns a list of "a leads to b" type statements and converts them into a graphics file like jpg or png. You can make the statement list with any plain text editor like "notepad" or "vi". Things really get interesting when you use dot to make scalable vector graphic files or SVGs. Firefox renders SVGs out of the box and IE with a little help from Adobe. SVGs can be hammered with Inkscape and they are humanly readable (if not necessarily intelligible) text files. The Gimp will also import, but not manipulate.

I got into "dot" looking for a way to draw an organization chart for a fairly large local church. Even with pencil and paper, the addition of one new person in the chart often led to crossing lines, long loopy lines, erasures and instead of art, I had graffiti (think worm eating spaghetti). The church organization chart was supposed to inform work flow for a new Drupal website and I decided to draw a DAG of Drupal installation.

Drupal looks deceptively simple but there are devils in the details. I am reminded of them every time I build a new Drupal site. Leaving off the details of building and connecting the server and its software at the front end and adding content at the back end, I wound up with a chart which overflows the screen and doesn't fit on an 8.5x11" sheet of paper. One fellow cleverly suggested putting links on the terminal nodes which lead to more graphs. Dot does that.

To create the SVG file, I entered the following command:

dot drupal.txt -Tsvg -o drupal.svg

You can see the results here.