What does Royce 1970 suggest about drawing node-and-arrow diagrams?
1. Learning happens through repetition and emphasis. Royce kept showing the world the waterfall, so that’s what the world remembered. Royce *didn’t* keep showing a vital part of the solution (iteration), so that’s what the world forgot.
2. There are certain visual patterns humans tend to find appealing, and others we find offputting. In figures, make the solution appealing and the problem offputting, not the other way around. Royce’s solutions have messy solution icons surrounding the pleasant-looking tidy problem.
3. I have no academic support for this claim – I haven’t looked – but I think people handle complexity better in text than in diagrams *when it comes to grasping the totality of an argument or depiction of reality*. The Structure of Royce’s Argument is clear and linear, which is not what the figures imply.
The problem with diagrams is that they’re branchy. There are multiple paths, some of them just there for completeness. Unlike a narrative that’s read linearly, the user of a diagram has to pick the order in which to read it, which means the diagram has more opportunity to fail to convey what was intended. I speculate that’s why hypertext fiction has never really taken off.
If you must use a diagram, I have two suggestions:
1. A diagram should contain *only* the nodes and arrows that are necessary. Zoom in. Forget about progressively building up a complete solution: focus a diagram narrowly on the current topic. Of Royce’s five solution diagrams, only one (Royce Diagram 7) benefits from showing the waterfall.
2. If you desperately want to culminate in a picture of the whole solution in all its glory, *build* the diagram rather than *show* it. I learned this from Michael Feathers. I was complaining about a complex UML diagram. In response, he built it up gradually on a whiteboard, explaining each new node and arrow as he added them. I understood at the end. That’s something like what Royce was trying to do, but the need to flip pages and rotate some of them because the diagram was too big to fit horizontally, plus the difficulty of locating the nodes under discussion (as opposed to Feathers’ just pointing at them or drawing them in) adds too much friction. Paper just doesn’t have the right affordances for complex diagrams.