As in any kind of programming task, neatness counts. Classes in Swarm are created with methods that group together their jobs by functions. It is much better to write small methods, each of which accomplishes a relatively specific task. In order for data to be displayed meaningfully in a graph, for example, it must be provided to the graph object in a format that the graph object can handle. The class World in simpleObserverBug is subclassed from Swarm's Grid2d class.
Graphics are optional, but nice.
Commands in the Observer Swarm control the graphical display. There are many kinds of graphs and ways to alter their appearance. It is not necessary to design a Swarm program to make pretty pictures, however. There is a useful example of the batch mode in the Heatbugs code. Open Source means open the source.