[MurrayHill1980]

This is a very good point. In the early days of Graphviz we put a lot of effort into making very readable diagrams of fairly small graphs, mainly in drawing directed graphs (dot). We aimed at graphs with under a hundred objects. We agree with the viewpoint that it is better to apply some sort of analysis to reduce a larger graph to a smaller one that can be read and understood. People still want to draw much larger networks. In fact it is valid to want an overview of all the data, it's just not clear how to do this with many thousands of random connections. Graphviz sfdp (based on Yifan Hu's earlier work) and recent work on Maxent (which has a decent theoretical justification) and from Ulrik Brandes group are good examples. One reason graphviz neato does not make such great layouts of large graphs out of the box is that it is straight statistical multidimensional scaling, and we just drop shapes on top of the points, so they can overlap badly. We felt since people are relying on it for data visualization we did not want to post process the MDS layouts by default in a way that could be misleading. But you can turn on overlap removal (neato or sfdp -Goverlap=false). We really should document all this in one place that is easier to find and understand.

About the external shape loader issue - this code is somewhat centralized in graphviz/lib/gvc/gvusershape.c and in gvrender.c which calls it, and I thought it could be disabled at compile time (because we did address the security concerns at one point) and there's a lot of other machinery to control compile time features. Maybe John Ellson can comment here. Kudos to John for recognizing the problems with the shape loader as soon as I proposed it but apparently that didn't stop us at the time. Stephen North