Image_GraphViz is a class that provides methods to generate graphviz (dot) files. It also calls graphviz with all necessary parameters and outputs the generated image to the browser, or stores it into a file.
The package supports clusters, nodes, edges and all attributes to either of them. Apart from that, Image_GraphViz is able to store and load its own graph definition files.
While it abstracts the actual generation of dot files, one still needs to know the dot attributed graph language to take full advantage of the package - especially for style and layout adjustments.